You know, I've been digging into this a lot the past week or so. I'm starting to think the T5 preference is because of the design of a lot of the fixtures, and the bulb difference may not be that great. A lot of the quickie PC add-on fixtures that I've seen just pack a lot of bulbs into a tight space, plus have poor quality reflectors and ballasts in a cheap quality housing. I can see a lot of people getting a bad first impression from these housings and swearing of PC's for good.
The first thing I see referenced all the time in arguments is that T-5's use better ballasts. Yet, all of the GOOD ballasts I've researched can be used for any kind of T-8, T-5, T5HO, T5VHO, PC or T2's. So the better ballast theory falls flat right away. The includes Icecaps, which give PC wiring diagrams in their instructions.
The next argument I see is better reflectors for T-5's. But again, Miro-4 individual reflectors can be had for any bulb type. This is with the bend patterns for specific bulb types, not just using one reflector for multiple bulb types. Though I do admit that most PC fixtures do not have this, but it doesn't preclude retrofits.
That leaves just the bulbs. Numbers wise, the bare bulbs don't seem too different between T-5HO and PC's. After all, a PC bulb is a T5 bent in half. Lumen output for any given wattage bulb, when you can find it, is very comparable between the bulb types. 55w T5HO is given at 4500-5000 lumens, depending on the K rating. PC's of the same wattage have very close data.
I'm still trying to determine exactly what a T5VHO really is. Is it a different bulb? or is it over-driving a T5HO bulb with an oversize ballast? If it's just over-driving, has there been any testing of doing the same with a PC bulb?
But if there is one thing I never see anybody have, it's a good comparison test. If there is one, I'd love to see the data. And what I mean is a comparison using the same ballast, comparable reflectors, and bulbs of the same wattage AND color range. I've seen people say "I had a 4x55w PC and my new 2x55w T5HO's have more Lux/Lumens/Par". But what exactly are they comparing? Is it a JEBO PC fixture vs a retrofit T5/Icecap/Individual reflector? It's like saying "My Mustang beat a Corvette", but forgetting to add it's a Saleen mustang vs a 1978 base model Vette.
-Hans