Personally I prefer leather seats. All of my cars have had them for the last 20 years.
On a bike however, I would worry about the rain/sun killing the seat.
Another ex-Fazer rider that is a foccer again
(As you asked me on the other thread...) I've no experience of leather. I'm sure they are lovely, will get more comfortable with use and they look great. You'll need a decent stapler to fit it. I've recovered a couple of seats in vinyl and it's really satisfying.
Unfortunately my bike lives on the street in central London, so intentionally I don't want my bike to look too good or of any value as it will get stolen. I'm only refurbishing my seat because I tour quite a bit and it's particularly uncomfortable.
Brett
-suck-squeeze-bang-blow-