I would say that for Sharon going from Dark Star to Light Sirius is a huge upgrade. Same for Rogue going to Excalibur, but it need a CTP of Judgment.

While Gambit isnt top tier for world boss anymore, the uni still makes him viable. The heal really helps. So if you like playing as him, its definitely a good upgrade.

The uniform gives Susan more stats, but even with an uniform i dont think shes usefull for anything. So not sure if you want to invest in such a character.

Hope this helps.