We currently use BlackBox and they use their own techs where I'm at (Phoenix). We also used them extensively when I worked for Level 3 several years ago. As with anything, your experience with them will vary largely by location and can even vary within a market. I have dealt with some awesome BlackBox techs. And I have dealt with some really bad BlackBox techs. The guys I work with on a regular basis in Phoenix are great.
Do you know or have experience with either company? Do they have their own techs are they just bidding out for local techs in the area? I have work that needs to be done all across the US and just trying to look for some options.