In my opinion, the functional advantages/disadvantages between a rimless/traditional tank would be greatly minimized if it were possible to get tank manufacturers to build rimmed tanks in the manner they did in the 80's and 90's. That is, without the idiotic braces built across 4' and 5' tanks.
It's hard for me to say, since I don't design/build tanks, but it seems that tank manufacturers added braces across the tanks to compensate for using thinner/lighter trim and glass. I've a 90 gallon built in the early 1990's with no center brace, and the glass is a bit thicker than the equivalent tank built today. But what's really striking is the rim difference - my 90 has very thick/heavy duty plastic rim/base compared to today's tanks. And the old-school Oceanic Tek tanks that are heavily built and aren't braced sell for big money when they come up for sale, at least in my market.
To me, this is the primary advantage of a rimless tank - no center bracing. That's partly because I think the "clean and minimalist is aesthetically superior" thoughts that I see are silly; one could easily make the counter-argument that minimalism is austere and unimaginative. But in exchange for the no-center-bracing, one gives up a lot of design flexibility with a rimless design, since by necessity they're a good deal shallower than the depth that an equivalent length and width rimmed aquarium can be.
As an example, I'm debating whether to buy a 72" long or 96" long tank. Using Great Lakes Aquariums as an example, I can get either length in depths up to 30" with a rimmed design. But in a true rimless (no euro-bracing, which defeats the access arguments for rimless), the max depth one can get in 72" lengths is 20", and a grand total of 15" deep in a 96" long tank. To me, that's the equivalent look of a glass kiddie pool.
