If you want to get in to the gritty details, you can start
here .
The FRC cRIO-II has twice the memory: twice the RAM, twice the FLASH, and twice the on-die cache in the processor. However, raw execution speed in the cores are (roughly) identical: both run at 400MHz and can issue up to 3 instructions per clock.
The extra memory is good for vision, but won't really affect things like trajectory calculations and PID loops. Simply put, anything that the PIC could do is trivially small on the new system. Bumping the number of PID loops from 8 to 80 would have no impact on performance, but bumping the image size from 160x120 to 640x480 certainly will.