What's better on the XT925:
-screen - AMOLED (vs TFT on SP)
-battery - the xt925 is 2500MAh (vs 2300 on SP, not much, but every bit helps)
-secondary camera - 1.2mpx (vs VGA on SP; this may not seem important but everyone uses the "selfie" cam from time to time and the difference between 0.3mpx and 1.2mpx is HUGE)
-internal memory - XT925 has 16GB (vs only 8 on SP)
What's better on the SP:
-the chipset is newer, most notably the GPU is better - if you're into some hardcore Android gaming, then the SP is for you
If you're not into gaming, I think XT925 is the clear winner. I don't know how the SP development is, but you can unlock the bootloader on the XT925 and the availability of ROMs is great. There are multiple maintainers of CM12 for it and the ROM runs freaking great.
Put up any specific question if you've got them! For me, the XT925 is one damn good looking device, too. All the Droid RAZR series phones are freaking great looking. But that really depends on taste... Although, each time I pull it out, people still go "woah"
