You're comparing a groupsets that aren't even equal. Force is better than Ultegra.

Ultegra is to be compared with Rival.

However, go with whichever you prefer. If you like SRAM's double tap go with it. If you like how smooth Shimano is, go with Shimano. Neither one is going to make you go any faster.

I personally like SRAM because of the double tap, the smaller shift levers, and the feel of the shifters. SRAM products are also lighter than Shimano.