Tis a toss up this one.
1.9 - Solid engine, on the 150 the camshafts are a weak point but other than that there is not a lot to go wrong. Has a DMF which can go bang, and will cost near to 1k (depending on where you go) to fix it. Limited to either 115, 130 or 150bhp versions. I found the 130 to be best blend.
2.0 - Similar engine, dodgy injectors and DPF filters can play up a lot. Same with the DMF as the 1.9. The upshot is you can either get the 140 version or the 170. They drive a hell of a lot smoother as well. Power delivery is a bit more linear once on turbo as well.