Well, the G34 does come with adjustable sights, extended controls and a factory 3.5# trigger. That's $30.
I honestly can't say there is a big difference between the two models (for me). In terms of performance, I have noticed a better recovery between a G22 and G35, but the G17 and G34 don't go the same way for me. Even at that, the difference is neglible--if you're going for that 'last 5%' of your performance it might matter (in that case buy a Bedel).
IMHO,
Dan