Seeing as this is a seven month old thread, I don't think what I say matters, but anyway..
It depends on a few things.
The 1.8t is a nice engine, surprisingly nice for a turbocharged four-cylinder. If your friend want too keep the Golf feeling, swap in a 1.8t.
But if he on the other hand want a cruiser, get the VR6, the power delivery is so smooth, it pulls hard across the power band and makes a nice sound

It does however cost a lot of money to get any more power out of it.
So basically it comes down to two things, money and weight.
If he hasn't got so much of one of them, and don't want anymore of the other, get the 1.8t
If he has a lot of one, and wouldn't mind some more of the other, get a VR6.