Lots of valid perspectives here.
For me (best qualifier I can come up with!), it comes down to trust in a person/firm's ability to improve in a direction coherent with your own desires.
I own, and have owned, a number of pieces of gear modded by a particular person/firm. I started by buying a used unit, and liked it, so sent it in for further mods. Liked those, so worked with that individual/firm to upgrade another piece of gear. Later, when new technology emerged that interested me, and knowing that the trusted (for me) indivudual/firm worked on that kit, I sent that piece over (drop shipped new) and had it modded. Have subsequently had it modded again by same individual. Still using that same piece years later, it is at the heart of my system.
So, for me, it comes down to trust earned.
Not sure how it helps you with your considerations, but those are my comments about my own experience with one specific "modder" across 5+ pieces of gear, over the past 4-5 years.