To the original question, a spiral bit (up or down) is somewhat better than a straight bit. As to the best brand, if you are doing no more than 10-20 boxes, most will be ok. Whiteside and Amana are better in terms of longer life and the ability to resharpen more (straights only, though). Freud is a reasonable compromise. Then Rockler. I'd put Yonico and MLCS at the next tier down and anything made of NoName Chinesium at the bottom.
As to the best way to do box joints, they all work just fine if you use care. There really is no "best" way - the best is the one that works for you. I think my results back this point up.
I use an LS positioner to do mine on the router table with a straight bit. For hardwood and softwood, no fronter, just a backer needed. For plywood though, a front and back are needed, even for top quality baltic birch ply. That stuff splinters if you look at it sideways. The trick to avoiding chipout is to enter slowly. (there's a joke in there somewhere...).
By the way, make sure you put your bit as far into the collet as you can (minus a tiny amount to avoid bottoming) - this will minimize runout that could make for an oversize cut and loose joints. I learned that the hard way - somewhere there's a box that is 1/2" smaller than I had planned.
