Hey, buddy!
Good questions - definitely check out some of the other threads here on this forum that have addressed the same concerns/questions.
Regardless of where you look on the internet, there always seems to be a large, minority group of divers that tout backplates and wings. Those who do a lot of diving, especially, tend to gravitate towards them. In fact, it seems that there are really two groups out there regarding backplates and wings: Those who love them, and those who haven't tried them.
Here's a list of small advantages and disadvantages to backplates and wings:
Advantages:
1. Backplates and wings are completely modular - that is, you choose the setup that you want, and assemble it yourself. There are literally dozens of companies out there making parts for backplates and wings, which are completely interchangable. Thus, you can dive a "simple rig" when you're in a pool and get as "sophisticated" as you want when doing serious, demanding dives. Almost all rebreathers utilize a backplate and wing as a basis, and backplates and wings support doubles systems as well as they support singles systems, with or without countless modifications. For what it's worth, most BC's do NOT support doubles systems (there is only a handful that do), so if you ever plan on diving doubles or rebreathers or sling bottles or scootering, a BC will either not work for you at all or work only moderately.
2. Generally speaking (there are alternatives), backplates and wings utilize a single long piece of webbing to create the harness, which is totally custom-fit for you, by you. Fitment is always perfect and totally custom, because you made it that way. Some plates are now made in "small" and "large" sizes, but it's a misnomer... Plates are sized to fit tanks, not people - so a standard-sized plate is the way to go regardless of your size... And you make the harness the size that you want. Aside from the perfect fit offered by a backplate and wing's custom harness, the entire harness can be replaced by you in a matter of a half hour or so - so a few years into your diving when your harness is all worn out, the entire thing can be replaced for less than $20. Try that with a "BC."
3. A stainless steel backplate resting on your back is remarkably comfortable, especially when worn over a wetsuit. Yes, it looks gnarly, but they are far from it. Instead, they offer stability and security for your tank(s) and the rest of your rig that is unmatched by a "these four to six sizes of BC fit everyone perfectly" BC. Dive one, and I'm sure you'll agree.
4. Many BC's are measured in terms of "inherent bouyancy" - that is, they're all slightly positive, meaning that they ADD to the amount of weight that you need to be correctly weighted in the water. A stainless steel backplate is quite the opposite - not only does it have no inherent bouyancy, but it's actually
negative in the water - meaning that you can usually take 6-10 pounds off of your belt as compared to the same dive in a "standard" BC.
5. Wings are interchangable, as they all have 11" "centers" (the holes used to bolt the system together). You can choose a large wing for when you need it (doubles, steel tanks, drysuits, cold weather) and a smaller, simpler, much more managable wing for when you can get away with it (single aluminum tanks in tropical waters and/or traveling).
6. Performance: Nothing on the market - ever - has been as streamlined and balanced as a backplate and wing. For more information regarding this phenomenon and why performance is so astounding with a backplate and wing, see an article I wrote years ago for the DIR Explorers group:
http://www.deepsouthdivers.org/old/homebc.html (Note that the beginning sentence in the third paragraph asks the same question that you did, above...
)
Disadvantages:
1. Backplates and wings can be intimidating to a lot of people. They look like the serious dive gear that they are, and not like "beach toys." With many people attracted to scuba for the "beach toy" slant, many people will simply move onto something that they consider "friendlier."
2. Backplates and wings take several dives to get adjusted properly. Unlike most BCs that simply require you to pull down on a couple of straps to adjust "on the fly," backplates and wings demand to be adjusted between dives for the perfect fit. This makes them a poor choice for rental gear, but an excellent choice for personal gear, since the lack of "on the fly" adjustments also means that they keep their correct adjustments over time and do not need constant attention on every dive like a standard BC will. Lately there are several offerings in the marketplace called "deluxe harnesses" or "adjustable harnesses" or "Infinity" systems out there, and they are blurring the line between "quick adjustment" and "permanent adjustment." However, all of these offerings, while more easily adjusted, add to the complexity of the rig and detract from one of a backplate and wing's major advantages - the simplicity and infinite adjustability of a single piece of webbing valued at about $20.
Unlike claims, there is no significant difference in "comfort" between padded straps and non-padded straps if you're wearing a wetsuit. In fact, to a degree, padding offered in many "comfort" designs can actually detract from the rig's feeling of solidity.
I have heard that padded straps can be appreciated if you dive without a wetsuit at all - for example, in a T-shirt or shirtless. I don't know why anyone would ever do that, however... Even the warmest water still makes a diver cold after an hour or two, and the water's filled with all sorts of stingy, pokey things that a wetsuit can protect you from.
3. Cost: Initial costs for backplates and wings are usually about the same as some of the best offerings in the "standard BC" marketplace... Usually ranging from about $500 to $800 for a comparable, well-equipped highline BC. However, true cost-of-ownership for a backplate and wing can actually be much LOWER than that of a standard BC, as resale values for backplates and wings rarely dip below 50%, even for a several-year-old system. Contrarily, standard BC's typically lose about 50% of their value the first year, and usually bottom out around $75 or $100 several years later, depending on the BCs condition. The difference is due to the ruggedness and life expectancy of backplates and wings, and the fact that their design changes little from year to year.
If initial costs are a concern, consider the purchase of a 2 year-old backplate and wing. It'll last literally a lifetime, work for all kinds of diving (and support you as you grow in diving), and hold much better resale value if/when you go to sell it. Backplates and wings are generally available on the used market on eBay, or on ScubaBoard's or TheDecoStop's classifieds section.
Knowing you and your size, I would recommend a Koplin plate available here:
http://www.oxycheq.com/Wings-BackPlates.html Look for item ROWB-01-02. I also recommend item ROWB-03-03, which is the harness, D-rings, buckle and crotch strap (don't let the crotch strap scare you - they're awesome). Specify that you want a 15-foot piece of webbing instead of a 12-footer, just in case you need it to accomodate your size. Lastly, pick up a "Light" single tank adapter (item number ROWB-06-02) here:
http://www.oxycheq.com/Wings-STA.html .
The only things you'll need in addition is a wing (my favorite is Halcyon's 30-pound Eclipse wing - purchase it from my buddies Doug and Andrew at Extreme Exposure in High Springs -
http://www.extreme-exposure.com/product/bc/wings ) and a set of cam bands (these, which don't need to be wet to work, and come completely apart for very easy changing of tanks:
http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=ScubaMaxTankStrap ).
In all, what I've just recommended to you will be pricier than your buddy's "half off" BC, but will be something that you keep and use for all of your diving for the rest of your life, and serve you much better than any BC ever could. It'll also have a much better resale value if you ever decide to stop diving.
Hope that helps.