Is there a difference between the STB's that bolt on with four holes vrs the two holes on each tower?
Yes. I had the FRPP Boss 302 brace on my 2010, and it uses 2 x slots at each end of the brace. Those 4 x bolts at each strut are only 26 ft lbs...dick. My problem with the slotted STB's is.... it's not solid, with 2 x slots at each end of the brace..and a paltry 26 ft lbs. One good smack, and they will shift on you.
I replaced it with the STEEDA STB. (boss 302 STB would not clear the roush M90 blower, so after blower installed, the boss 302 STB had to be removed). I also installed STEEDA HD adjustable strut mounts, which allow for camber adjustment. (then set the camber to -1.5 degs on each side).
The steeda STB uses all 4 x holes at each end. The steeda uses holes, NOT slots. The reason for the slots on the frpp STB's is simple, their length can't be adjusted. On the steeda STB, they use spherical's on each end, and the overall length of their STB can be adjusted, with lock nuts on the CM threaded ends....just like a turnbuckle. One end is reverse threaded ( just like a turnbuckle).... so the overall length adjustment is easy. With 4 x bolts, into 4 x snug fitting holes...at each end, it's bullet proof, it can't budge. The steeda STB is designed to work in conjunction with the steeda HD strut mounts.
Another advantage to the steeda stb is the transverse bolt can be loosened at both ends, and transverse bolt removed at say driver's side, and the STB can be swung up. I had to do this to gain clearance when I swapped out the oem twin 55 mm TB with the bigger FRPP twin 62mm TB. Also had to swing the STB up on driver's side to gain access to plug #8 (driver's side, closest to firewall).