As your score is of 170 marks in IIT JEE 2010, so with these marks your estimated ank would be some where in beyond 8000. According to the calculation chances are less that you can get your expected branch in IIT's.
Now if we talk about your ISAT score then hopefully you have cleared the cut offs of this year, and if you manage somehow to get through ISAT then defiantely you should prefer it rather than IIT.
However score may vary and as a result rank may also vary, a slight difference may create lots of difference in rank.
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all the best.
thanks and regards.