If this is something you are going to be doing routinely then pick whichever one you want and stay with it. Assuming they are doing their work properly, consistently, you can more easily compare results. So use the same vendor.
I've used Oceamo (2 times), and ATI (21 times). Both provided consistent results. I've also used their support services and in both cases they responded within 24 hours. Both had similar turn around times ranging between 7 and 9 days respectively. I'm located in California.
Obviously I used ATI more so may be a bit biased towards them but honestly I don't think you can go wrong with any of the 4 typically mentioned these days. Oceamo is a little bit more involved with the forum here and has answered some questions. Not sure if that makes them better than the others though. Whatever you choose if it is something you are planning on doing routinely though I would pick one and stay with it for data comparison.
- Triton
- ATI
- Oceamo
- Fauna Marin