R32 will be far cheaper to maintain but I think you'd be disappointed.

Had a mates R32 for a while when he was working abroad and it's lovely to drive but isn't really that quick in all honesty. Think the noise makes you think it's faster than it actually is.

Also, the Mk5 R32 looks wank compared to the Mk4 IMO, the styling is better on the GTi at that age I reckon.

M3 for me but seriously look into the running costs - a couple of pals have not done this and had to get rid of them due to some nasty bills.