As usual, there's a few different things going on all at once, which makes the picture muddled.
The profound difference is between IBM caps (whether one or two piece) and Unicomp's. The legends are just night and day, there's really no comparison. Also, Unicomp's colour matching for IBM's original colours is quite noticeably off. Don't try mixing Unicomp pebble with IBM mods.
Then there's the difference between one and two piece caps. That's a tighter race. Naturally, even Unicomp still makes single piece caps (just look at those 2.75 unit Shift keys) and theirs match their two piece alphas fine enough. The trouble kicks in when you try mixing, again. IBM's one piece alphas are noticeably shorter than the two piece versions. Put them side by side and you will notice. Even if you're Chyros!
Model F caps are the best when it comes to printing. XT legends are so bold and rich you can really see the corners IBM cut when you put them on an SSK like I did, alongside its native IBM mods. I also found the height difference was very much in effect, which isn't enough to make me stumble as a typist but it is annoying all the same. So long as it's between alphas and mods it's understandable, but just you try to handle the XT's missing single unit ] key. Ungh!
I'm glad I have the original caps on my Kishsaver. They're Model F awesome, without the layout bamboozlement of the XT. I put a Unicomp red Escape on it, which is bearable enough in blank. But just the thought of a whole set of Unicomp's on a board as special as that? No thanks.
Though I can live with the RGBs…