Yeah, J-bands are great.
Good point....I have been out places and not had a place to hook them up, doesn't happen too much. I know my sons team have a "pitchers bag" where the team keeps a foam roller, a set of bands and a couple of 5 lb weights.
Now that I think about it, the older he gets the more stuff we end up hauling around haha.
So it goes I guess. Wouldn't hurt to carry both around. My son keeps an extra J-band in his car at all times in case as a back up.