Smaller targets are better for bearcharge. In this sense it's different from bash -- bash, you ideally want to be 1 size bigger, but 2 sizes and you can't bash. Bearcharge, bigger is always better.

I imagine the ganging-style difficulty mods are pretty similar with bearcharge vs. bash.

Weight I'm not sure about, but my rangers never whored out weight and my impression is that bearcharge is a lot better than most rangers seem to think it is, so I'm guessing it either doesn't matter or it doesn't matter an enormous amount.