I can't imagine why you wouldn't buy one from TPM. This is their bread and butter gun, they build and sell tons of these things and they put hours and hours into each build. They are the MPSD experts, this is their world.
^^THIS^^. That guy who posted all over HKPro about an issue he had with TPM is a crankcase and if you read that thread you'll see what I mean.
TPM did my MP5SD build, to my specs. (get the welded rail unless you just have to have the classic look.) It's PERFECT. I liked it so much I immediately ponied up for one of the barreled receivers to stash away, ("two is one, one is none") even though it was $1K more than the Atlantic Firearms/Todd Bailey product, which has had issues. ("Why won't my suppressor fit?" LOL)
I can't even Imagine paying ANOTHER $1K over the TPM Price for DT (admittedly no familiarity) or anyone else. There's no need to.
I would also go TPM if you’re looking for a custom gun.
But going after the Omega product is disingenuous. In that first batch of a dozen or so there were a couple reported cases of the cage being off axis, and then there was one moron who bitched that his “favorite” 18x1mm Omega 9K didn’t fit because he didn’t understand what an SD can is, and refused to admit his error and blamed Atlantic’s wording.
Since then I’ve seen nobody complaining about the SDs and everyone seems to report that they run very smoothly and reliably. Personally mine has run without a single failure over the first few cases of ammo.
I was originally going to get a TPM to back it up, but it’s so smooth I’m going to do a 53 from them instead this summer.