Your rifle is already shooting quite well so maybe your money is better spent elsewhere; optic maybe. But, with your two options I say arrel. And my vote is X-Caliber. I have 4 and they’re all fantastic.
Of note, I have replaced an accutrigger with the Timney replacement which is a fine trigger but not enough of an improvement to warrant the cost. Now the timney replacement for the old three screw triggers is a different story though I have also tuned factory three screw triggers to be very fine as well.
I concur with the part about how it's shooting good already and not going about messing with success.
I also think a good optic can improve the rifle's utility; but I'm not talking about pricey precision optics. I'm trying for something (perhaps...) a bit more practical.
Of late, I've been experimenting with the Bushnell
AR Drop Zone BDC optics. I have them on several bolt guns, including a Mossberg MVP 223, and a pair of Savage 11VT's; a 223 and a 308. I also added a 308 to my 20" PSA PA-10, and am thinking about getting a few 308's for my 6.5 Grendel Uppers, since so much of the internet buzz suggests that (at least out to 400yd) the 123gr 6.5 Grendels shoot pretty much the same trajectory.
My 11VT's are identically configured, except for the scopes and chamberings, and I suspect they also have the same Choate Stocks as you mention. I've added Choate LOP extenders and Hawkeye adjustable cheek rests.
Lately,
BDC versions have appeared for the 6.5 CM, as well. The prices on them are not bad at all. They use a side focus/parallax, which I also like.
After zeroing, and at known distances, one can rattle off hits at 100yd, 200yd, and 300yd quickly. I'm hitting the three distances on steel in well under 1 minute, and sometimes under 30 seconds. If I had steel all the way out to 60, I'd expect they'd be covered, too; but I'd be a bit less hasty. I use a 600yd LRF, and although I haven't used it yet for this exact application (except for the Mossberg), it's not a stretch.
It likes particular loads, but they're ones I like anyway; 223 55-62gr, 308 168gr.
Anyway; I believe it's worth suggesting.
Greg