geekapproved :
It has 48 less SP's, and the benchmarks show a pretty big difference in gaming performance. I think your reading the heavily overclocked GTX560 vs. GTX560ti (stock) benchmarks, which can't be compared because the ti can be overclocked too.
The 560ti competes with the HD6950 1gb, the GTX560 competes with the 6870.
In the THG review I linked above, THG had the "clock speed set to reference specification for reference benchmarks" for both the 560 and 560 Ti, as stated on the test setup page:
http://www.tomshardware.com/reviews/geforce-gtx-560-amp-edition-gtx-560-directcu-ii-top,2944-4.html
The benchmarks show little difference in gaming performance - I refer you again to the THG review I linked above and as noted below with the non-Ti listed first:
Crysis 2 - 63.2 FPS vs. 66.9
Bulletstorm - 55.4 vs. 53.9 (non Ti actually wins this one)
Metro - 67.3 vs. 74.7
Loar Planet 2 - 64.3 vs. 70.6
Aliens v. Predator - 64.9 vs. 72.8
F1 2010 - 50.9 vs. 54.8
Just Cause 2 - 59.6 vs. 65.9
HAWX 2 - 115.0 vs. 124.0
Those are not big differences in gaming performance. And for both cards the minimums were pretty close to the averages. So most likely the differences will not even be noticeable while playing a game. So you would pay about 23% more for a 10% increase that will most often not even be noticeable. But as I noted above, it is a matter of personal preference if it is worth it to you.