My own experience:
Frank Thomas – pretty decent off the shelf leathers, the one piece I had was fine, but had quite a bit of extra material in the arse area, the price was good at the time (about £450), I later decided that I wanted a bit more convenience so sold them and got a two piece set – again good quality and fit, and other than being cut off in hospital they stood up well in a crash.
BKS – my second two piece, and frankly, they were pants – I had the correct size but the jacket was far too tight on the chest and the waist zip was difficult to do up, you also couldn’t mix and match this set as you could with the FT stuff, so I wasn’t able to get a large size jacket (next size up was a bit too large though!). Sold these after a few thousand miles in the, at quite a loss (lost about 60% of what I paid for them).
Berik – my current leathers, and frankly, the best I have ever owned. These are a two piece again, and like the BKS ones are missing the outside pockets, meaning everything is stored on the two inside ones. The leathers are off the shelf ones again, but fit amazingly well, easy to get on and off with comfy fit and hard wearing knee sliders (the FT ones disintegrated pretty fast).
Before choosing the Berik ones I looked at many other brands, Alpinestars were similar quality, but carried a higher premium, likewise the Dainese stuff did too, RST was cheaper however, but the armour seemed far too soft to me.
If I were in the position to buy another set, I would probably go for a one piece as I already have the two piece – if I were to only own one set though, it would have to be two piece, they are very secure so wont part in a crash and you have the added benefit (most of the time) of better storage and the ability to take a dump without being a contortionist
Scort.