What time lapse are you talking about? The one year in Limit Cut? That's hardly enough time to get used to their clothes. Phase 2 began at end of KHIII + Re:Mind.Well in my case there's two reasons for voting for them.
I don't really like Xion's outfit that much, besides always saw her as a pants kinda gal, her black top and white skirt don't quite work for me. Similarly with Axe,l the lack of real color in his new wardrobe was rather disappointing.
The other reason is how this was phrased, it's asking "who should get new outfits in the new phase" my answer to such a long period (going of the last one) is everybody.
While I respect personal preference, there's no real good justification why they should be picked over everyone else when they have new outfits, whether one likes them or not. We got Ms. White Rag For Years, Skater Boy 2000, and Feudal Era Japan clan to be more concerned with.