The TSX-R supposedly is compatible with more applications. And the lenses are slightly different, so maybe there are some cars the FX-R won't work with. You have to mod the projectors slightly with the TSX-R and remove part of the cutoff shield. At least on the first gen post recall projectors. From what TRS told me, the FX-R worked great with the pre-recall projectors but would need mods to work with post recall so there is a difference. They also told me that the FX-R was a really low seller and it took them forever to sell out.
So now the question remains...has anyone tried both on the 2nd gen headlights and which one looks better... If only I had a spare headlight I could do the test, I have access to both lenses. To be honest, I wouldn't be surprised if the 2nd gen projectors were the same post recall 1st gen projectors...