I recommend maxmax.com over competitors, I know that his website isn't as good looking as lifepixel's but the work is first rate, call and talk to Dan and you'll get a better understanding of how things work. He's easy to reach and you'll need him if/when focusing issues occur. Unlike lifepixel that ties you down to some zoom, maxmax's conversion works with a wider variety of lenses and if you wanted you could customize your focus for one lens.
I had the opposite experience. I had my first conversion done by maxmax, and, despite all their "clean room" claims, it came back with a great deal of large crud stuck to the sensor that I couldn't clean off. I sent it back to them for cleaning, which they did, but not very graciously or apologetically.
The second time I used lifepixel. Perfectly clean sensor afterwards, and they even put a very useful custom white-balance in the camera memory that maxmax didn't. Between the two, I'd far more recommend lifepixel.
I'm not sure what you mean when you compare them regarding the focusing issues. The conversion people (either maxmax or lifepixel, both) can either tweak the IR focus to some generic average setting, which will be approximate for most things, or you can have them adjust the focus more precisely for the particular lens that you most use. At least that's how I interpret what they do - if it isn't, please enlighten me as to how maxmax can perform that magic better than lifepixel, since it isn't clear from how you explain it...
I recommend carrying two cameras, one color and one converted to IR, rather than fiddling with filters and not being able to see through the lens. I've done it both ways, and the former is far more pleasant and reliable. The way I do it, the only extra item to carry is a camera body - you can use the same set of lenses on both bodies, so it's not much more to carry.