Given that the two highest-profile examples of decolonization without uti possidetis are India-Pakistan and Israel-Palestine, my first instinct is to say that widespread use of the practice would lead to worse conflicts. On the other hand, it didn't work out badly in Micronesia, the Gilbert and Ellice Islands, the Comoros or the British Cameroons.
At a guess, I'd say that partition or consolidation of colonies can lead to improved outcomes if there's a democratic decision in favor, clear and obvious boundaries (IMO it's no accident that three of the places where it worked well were island groups), and guarantees of safety and civil rights for those caught on the "wrong" side of the new border. Otherwise, abandoning uti possidetis would only restructure post-colonial conflicts rather than resolving them.