I’ve had both, switched all of my rifles to the sopmod stock, fits great, comfortable and it looks good.
One of the actual learned souls at a local shop suggested the B5 as an upgrade from the standard M$ style stock. I prefer the look of the Magpul CTR. I do think the B5 would allow for more stability, and thus it will likely be what I upgrade to when the time comes.
Judging by the 3pages of responses, I am probably in a little late, but I put SOPMODs on all of my standard 14.5-20" rifles while I use CTRs on SBRs. Don’t really know why but that is always what happens. The CTR seems a little smaller than the SOPMOD so when I am going for that compactness on a rifle, I go CTR. I have never really thought to look up dimensions but thats how it seems just eyeballing it. Both are excellent stocks so you can’t go wrong. I have only owned I B5 and it was very similar to my LMTs… I could tell a difference bc of the texture but for all intents and purposes, they seem equal.