Too many Helicopter Operators want to use their own Check Airmen and thus avoid Third Party evaluation of their crews.
I've received training both ways, and must say that with one exception (a military support contract), the better training was with company Check Airmen. They knew our SOP's, set a higher standard, and knew the areas we were working in.
I'm sure there is good 3rd party support out there, but I'll take in house based on experience.