Getting back into the game
Well, endgame wise the scales for necro and rev are a bit tipped like this:
WvW: Both wanted
PvP: Both good
PvE: Rev is mostly considered useless(not counting open world because anything goes there)
Builds-wise you can run power or condi on necro comfortably and power on rev. Do note that you will get a load of hate if you play power reaper instead of the viper condi build.
So to summarize(pve side because spvp &wvw everything goes): Choose a Rev and you’ll feel unwanted, atleast until Anet deems it appropriate to fix the class. Choose a Necro and be forced to run relatively boring(imo) condi build and you’ll have an easy time finding groups for stuff like T4 fracs(all that health makes you not die, low skillcap class)