I just bought a GSXR1100 shock for my 1G but have yet to install it, so the following is just thinking out loud.
The following are features:
Hayabusa (‘04 but probably the same for all years) $60 +/-
Proven link-type rear suspension with remote reservoir shock absorber - rear suspension features fully adjustable rebound damping and compression damping and spring preload
Ohlins $700 +/-
Rear Ohlins Shocks features remote or piggy back reservoir with externally adjustable rebound and compression for quick and easy damping changes. Threaded pre load allows the rider to set the sag with a turn of a nut. Fully rebuildable and tuneable
Proggressive: $400 +/-
Description:
Machined from aircraft quality aluminum. 5-position rebound damping adjuster. Internal bladder design to separate oil and gas charge. Velocity sensitive, multi-stage valving for consistent, controlled ride and great handling. 14mm Chromoly steel shock shaft
I would assume that the materials of both the ohlins and proggressive are superior, but adjustability does not seem to be that different.
Based on this and very limited knowledge, I would go for the Busa and use the rest of the money to do the forks (proggressive or racetech with gold valves). I was looking into Busa forks (very good deal on Ebay) but it seems overly complicated and expensive for the street (if not one of the coolest f'in mods) and I think that this goes for the Ohlins as well. Unless you have the resourses and don't care about the money AT ALL. But then you should do Ohlins front AND rear!!