I've now shot my 870 with both, they both stood up to a couple of boxes of target loads, and a couple dozen 00 buck. I like to look through the TRS-25, the Sparc looks cooler, neither are Aimpoints, both get some bad press, both get quite a bit of good press, Vortex=lifetime warranty, the Bushnell sits lower on the receiver.
If I had to pick for a shotgun, I'd say Vortex for the warranty; on all my other firearms I liked the TRS better.
I don't trust electronics on a scattergun, I just use the bead.