Given a choice I would always prefer a heavyweight over a featherweight. But there are serious disadvantages to it.

1: weight. If you are just 1 person building it 100kg of robot is quite a hassle.

2: transport. Heavies are bigger than feathers so you need a decent size car boot or trailer to move them. Taking a heavy on the bus or train is not really an option, some feathers are not even easy to take on public transport either.

If you have no problem with these 2 main disadvantages, Id go for a heavyweight if I where you. Otherwise for a feather.

The Dewalts are fine motors for feather and lightweight. For middleweight or heavy they would work if you use 4 or 6 of them, I wouldnt try it on 2.