In my opinion, I think I've tried both, it just depends on my interest in the sport I want to bet on. For example, if I don't know much about a sport but want to try it, and maybe I'm tempted to bet on it, or perhaps because I see others showing interest in it, but that rarely happens. Most of the time, I still make my own analysis when betting, I make my own decisions and I think about who has the guts to win. So yeah, maybe I can consider myself a bottom-up bettor too.
There are really sports that we don't know but others know really well, and we shouldn't follow them because the chance for us to lose is high if we will only depend on our own ability or instinct.
If you want to do it badly, then maybe you can be a top-down bettor for that game and do adequate research or analysis only to increase your chances of winning. Not only you but I think almost all of us already tried both of the betting types but we may have stick on one type only as the time passes by. Maybe only few left who up until now are doing both types because like the OP said or described, each of them has their own advantages and disadvantages.