Haha i've been wondering the same thing about those cards so i've looked around a lot recently
Honestly for what it's worth if you have the money get the 670 as it handles Anti-Aliasing a lot better than the 660ti.
On the other hand you could opt for the 660ti and spend the extra money on, say, an SSD or i7 instead of an i5 but if you want pure performance i'd say go with the 670 though be warned you won't see a massive difference.
Just so you know, with the 660ti power edition overclocking can surpass 670 performance!
But as i said, if money isn't concerned - get the 670!
Hope this helped!