I'm betting that most people are going to tell you that a spacer is a spacer.
I mostly agree. Personally I prefer poly over aluminum. I ran TF spacers for a while (for no specific reason) and was happy with them.
2012 Cherry Red JK
TF 2.5 Coils w/ Billstein 5100 Shocks
17x8 Black Rock D-Window Alloys
315/70/17 GY Duratracs
4:56 Gears - LSD in Rear w/ Ten Factory Chromoly Shafts
TF HD Diff Covers