honda calls their variable valve timing technology VTEC. suzuki
bandits are equipped with something similar, called VV or VVT, i'm
not really sure, but such bandits can be identified by the red
cylinder block cover.
bandits have fully adjustable suspensions, not sure about the S4s.
certain ver S S4s and 50th anniversary ver S have brembo front
brakes, and i think that's really cool.
if your friend is into naked streetfighters, has he considered the
yamaha XJR400? ohlins rear shocks, brembo pumps and R1 (dunno what
brand) calipers. there's also the ducati monster 400 as well.
if he's willing to sacrifice a little top end for better fuel
economy, a hornet 250 would do nicely as well. i guess he can't go
wrong buying a honda...
just my 2 cents... 
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Ain't I the fastest rider on the planet?!?! =P