Well i own a 92 Cooper, and i'd say that it would certainly give a cinq a run for its money. If memory serves me correctly i've good a book somewhere with a magazine road test back in early 90's with the mini against the 205 and the cinq. I'll look it out.
Don't know about stats, but my mini has 72,000 miles on it, its not on its original engine (changed before i got the car), its on a low compression metro 1275 block, an SPi cylinder head, and HIF44 carb (all it all should be marginally below standard hp). It felt ok, i stuck on a stage 1 kit (manifold, exhaust, filter = £120) and had the car at a rolling road shoot out and it managed 59.5bhp. Which all said an done didn't seem that good, but it has peak torque of 68lb/ft at 3300rpm and it pulls like a train from 1500rpm all the way to 5500rpm. Can be pushed onto 6-6.5krpm but its not worth it power wise. Top speed was measured at 97mph as i asked the guy rolling roading the car to stop at 5000rpm.
A cinq would probably make a better day to day car, 5 gears, better economy, less rust prone? But the boot is no bigger, there is room in the mini for 5 strapping lads (been there, done that), and with a nice set of Cobra buckets in the front very comfy over a long drive, if a little bouncy.