Unless you have a ton of rare candy and 7-digit stardust, I wouldn't power up a lower-IV legendary just because of a particular active moveset (legacy move is a whole different story). If you have the rare candy for that, you should also have the TM's necessary to change the other one to your desired moveset, don't you?
If you don't have the rare candy but the prospect of getting it with your raid activity is promising, then it's the same conclusion: you will likely receive enough TM's to eventually change the 96% one to FS/Ovh.