I was in your position a few weeks ago, pondering the R32 vs GTI conundrum. I've been in 6 and 8 cylinder ///M cars for the last 8yrs so a move to a 4 pot was hard for me to swallow.
I went for the GTI for a few reasons.
1. Its a Turbo - I'd agree with people saying that 4 pots are sh*te (apart from Honda's mental Vtec -I had a CTR in my younger years) i'm an 80's kid, so anything with a Turbo is cool, end of. Personally I dont even mind a bit of lag, as long as when it does kick in it was worth the wait.
2. Its cheaper to insure, and run. Therefore better value, after paying to insure a 5.0 M5 while living in Zone 1 London, in a postcode usually on fire, its a welcome change to pay a reasonable insurance premium and to see double digit fuel consmption is a joy!
3. Evo Magazine (whom personally I value the opinion of) rate the GTI as a 5 star car and the R32 as a 4 star car. other than the noise, there is no real advantage over a GTI
4. Tuneability - the Mk5 GTI is easy to tune with endless possibilities. I bought mine already tinkered with and i have to say its hilarious to drive. Only yesterday i found myself in a big rush to get home for an Ocado delivery, so i took a very "spirited" drive home down some country lanes and found myself actually laughing out loud at the darty front wheel drive characterists and all or nothing boost of the turbo. took me back to my days of Renault 5 GTTs and Uno Turbos with bleed valves. i might even buy a non re circ Dump Valve for the comedic Wooopsht! sound on upshifts.
Yeah, OK sometimes I'm still a little underwhelmed when the TFSI engine chunters into life in the morning and sits there sounding like a sowing machine on tic over, and yeah i miss the totally ridiculous, thunderous, sound of my old stainless steel muffler deleted V8 M5 on a cold start.
But i can say in all honesty, that yesterday, i had the most fun i've had in a car for years.
Sorry to go on, just thought i'd stick my 2p's worth in.