I haven't done this myself but apparently the 70 series has a larger contact patch on the road when leant over but less stable than the 60 in a straight line. So if your main riding is in the twisties or the track then go for the 70, if your just cruising in straight lines the go the 60.
Heres a simple explanation of the different profiles
60 x section --> (
70 x section --> C
Also if you go to the 70 you'll have to raise the fork tubes in the triple clamps to suit the increased diameter of the tire (approx. 10mm).