I own both. They're very different balls designed for different conditions.
The Guru is a heavy oil ball. It needs significant head and mid-lane oil to keep from prematurely burning up. On any flatter PBA/Sport patterns 40 feet +, it's my first ball out of the bag. I really like the way the ball transitions from oil to down lane friction.
For me, the Yeti Uncaged is a good all around THS ball. I can use it on everything from light/medium to heavier/medium conditions. It's very versatile. I have pearls that are sharper when they encounter friction (i.e. Motiv Primal Rage), but I prefer the Uncaged for it's predictability.
I'm hard pressed to think where I would choose between the Guru and Uncaged. For me they respectively cover conditions that don't really overlap. If you have to choose, it really depends on what you see more often.