The 1.6 205 GTi for me.
Barely any slower than the 1.9, the engine felt lively and fizzy, and the 15" rims on the 1.9 dont suit the car at all.
I had a 1.6 205 GTi back in 1987, only had it a year, got a promotion and swapped it for a Golf GTi. The 205 was a giggle but the Golf was much better on longer journeys, my next one a 1990 16V (last of the small bumpers) had Recaro seats, power steering, a full BBS body kit, Ronal alloys and a GTi Engineering RE1900 conversion, it was pushing out about 165 bhp, quick in those days.
Mk1 Golf GTi is huge disappointment to drive these days (my pal has one) the brakes are the biggest surprise, the pedal feel is shocking.