I've had 10+ Thomson's over the years, as well as Chromag's, Hopes, Renthals, Funn, Ragley, FSA etc etc etc.
I like that Thomsons are stiff, silent and have never marred a bar or steerer. The Renthal in particular didn't meet any of those criteria. I broke one Thomson faceplate under warranty back in the 25.4mm bar days on a Titec Hellbent (?) before I had a torque wrench and used carbon paste. The M3 heads can be swapped out for M4s but with good hex tools (Bondhus or Wera) I've never needed to.
Syntace and I9 are probably the gold standards for stems, but my Funn stems have performed admirably especially considering the price from Aliexpress. They also have a good low stack height (30mm) option in the Funndruro. Not as pretty as a Deity but about a 1/3 the price.