Is there good reason to power up Level 20-ish 100% pokemon that are outside of the usual attack group, i.e. they're not Dnite or Ttars etc.? I've got a bunch of them that are sitting at level 20 or so, but have what I think are better alternatives that are already powered up. For example, I've got a 100% Poliwrath at level 20 with Mudshot/Submission, a potential fighter (with a couple TM's), but already have 3 93%+ Machamps at Level 35. Or, I've got two Charizards (Fire Spin/Dragon Claw and Air Slash/Fire Blast), but I have a 98% Entei with FS/O at level 31 and have a level 20 87% Moltres with FS/O that is sitting on 75 candies awaiting a reason to power up.
Other 100's at level 20 include Nidoking, Ninetails, Magnetron, Seadra, Arcanine, Misdreavus, Venusaur and Exeggutor (extrasensory/psychic).
The only 100's that I have powered up are three Gary's, a B/C, a DT/O, and a WF/HP, each to Level 35.
I have plenty of candy to power them all up, but don't know whether any are worth the dust investment. Are there future legendaries for which any of these might be useful?