The main choice is that you have to pick one or another planetary designation. Also, a planet full of lab buildings requires city districts (both to open the slots and house the researchers), which therefore aren't industrial districts, whereas you can squeeze a few more industrial districts on the planet if you're just focusing on alloys/CG. Still, I imagine the industrial+lab combo will be pretty popular, like it is already for ecumenopolises.
You can also put a bunch of labs on rural planets. Refineries and bureaucrat offices can go just fine on urban and/or rural planets, as well. Regardless of what kind of building jobs you want, it may be worth overbuilding city districts anyway, and/or putting down housing buildings temporarily if you don't have enough pops to work in all the buildings slots, because spare capacity will increase population growth.