Hey guys, I was planning on making a university and some UL related stuff on my homeworld to make it a bit more vibrant. But my doubt is: if there's an university in my homeworld, are my sims still gonna be able to leave for the UL's world for uni? Or will they have to attend in the homeworld?

Don't see why you can't have both. The sims you are playing actively can register for the Uni World one by phone, which will initiate a travel sequence, or for the Homeworld one by clicking on what will be the local Admin Bldg or its RabbitHole Rug.