I have watched with interest, and sometimes amusement, at several competitors' experience with aftermarket barrels.
The most successful experiences were with gunsmith (or shooter) fit barrels that were carefully fit to the individual guns, and then fed ammunition that fit the (generally) tighter chambers.
One individual bought the most expensive custom barrel available, then found his reloads did not feed reliably; so he chamber-reamed the custom barrel to fit his sloppy reloads, which put him back where he started.
In general , the drop-in barrels were little , if any, better than factory original.
Some beginning shooters were spraying bullets all over the targets, and any modifications they did were irrelevant to fixing poor technique.
I have both 4 1/4 and 5" barrel M&P Pros that are capable of 3" at 25 yds from rest, and for my purposes, that's fine. If you can do this and want to do better, you might benefit from an aftermarket barrel that requires fitting.
IMHO, save your money on drop-in aftermarket barrels.