750Ti every time, preferably in "SC" variant. Keep in mind though that even if you mine most profitable coin with it, current ROI per card is around 500 days.
that the number you get, if you don't try to think about what you mine... (using your brain helps a bit at that level...)edit: if you need 1 year and half to make 120euros... may-be it is better to stop mining...
you will probably make more with a metal detector on the beach... (or just saving one euro everyday... actually this solution will pay you 3 gtx750ti over your 500days)
Oh, I though the calculation was actually quite optimistic - 750Ti does about 2700kH in X11, 2000kH in X13 or so? At approx 60W @ modest 12 cents per kWh. If he bought the card today, the most profitable coins of the day this very minute are what - HIRO or RZR? Hashing power of single card will allow him to mine anywhere between 15 and 30 cents worth of such coins a day after deducting 17 cents of electricity? Each $169 card paid by 30 cents returns a day.... not very far off.