I'm not disagreeing with you on your points, but it's because of the switch over on the lower lines that makes the lower lines just that. As you point out you won't get the warranty if you're a home painter without the certifications anyways. The point I was making was that even given the warranties, the warranties are backed on the higher line products for a reason. You're not going to find a PPG certified collision shop using the lower lines on Pro-shop collision repairs, even though the name of the game is to reduce overhead and increase profit. Not if the shop is honest and really does want to stand behind it's Pro rating.
Global was all the rage just five years ago. Expect for the ability to mix the base with the clear for jambing I was never impressed by it, simply because as you pointed out, according to my rep a lot of it was Concept relabeled. And I've had my rep tell me which Shoplines are really relabeled. But he can't tell me which one's I'll get the desired results out of. The quality control on the lower lines isn't represented like they are on the higher lines, relabeling or not. And that's coming from a Platinum supplier I've done business with for 20 years. I'll trust his word.
I've never really been impressed with the lower lines, even Shopline, because of the flow characteristics. Given the same temps, humidity, air flow, I've had the bases do different things than the last batch. Same way with the clears. But when you pull the trigger and have to start playing with the gun to get the proper flow-out and it's at the exact same settings you used the last you spray a given product can make for a long day, because you're now having to re-adjust to something that isn't acting the same way you used it last time. Omni, as you pointed out, is notorious for this. One time it might flow like water and lay in like glass. The next time, your gun might be at the same settings you used the last time, but it's flowing like molasses. Speed up the gun, fly low, slow down the gun crawl like a turtle. Shopline, at least, you might run through four or five batches before you have this happen.
At least with 2002, I know given a certain reducer, using DCX 61 or DFX 11, I can pull the trigger on my gun and know how the clear is going to act, the first time every time. And it's usually because of the consistancies of the higher lines you see the Pro shops use 'em, too. The boss doesn't want the painters to have to relearn the product every time they paint.
I think one of the things you and I will point out, though, for everyone: make friends with your paint supplier. Tell him what you've got cooking, what your desired results are, and what your budget is. Find one you can trust, who's been in the business for a quiet a while. I would recommend a body shop supplier, not a parts supplier, because the training on paint products for a body shop supplier is there, not necessarily so with a parts store selling paints.