I haven’t seen that much Gundam, but I think most/all Gundam have wheels in addition to legs. I guess it’s the best of both worlds. Wheels are best for even terrain, and legs enable traversal of uneven terrain and jumping. In fiction of course. In real life, we can’t build anything that complicated.
I’ve always liked underscores better because it differentiates from the file extension. It just makes sense. Except it is a wider character, so it’d be longer.