I'd definitely be torn between the two. Luckily I ended up getting Sage Naruto before the Kage Treasure dropped so I didn't have this issue. I love using Naruto in quite a bit of my teams, despite him being such a great Ninja there are a lot of people on my server who don't even use him anymore and are mainly using ninjas from the Kage Treasure.

I would probably focus on Kage and just keep piecing together Sage Naruto throughout events and what not.