I have three 10/22's and two 15-22's. As mentioned both are unique and really not much comparison in common. In pure fun factor though, I'd give the nod to the 15-22. It cost more to get in to, cost more to shoot (this is subjective, but it's easy to rattle off 25 rounds knocking targets over with as it's just a lot of fun. Reliability goes to my 15-22, I don't blame either rifle, it's more the ammunition, the 15-22 just seems to get along with a little wider variety. Having said that, I've landed on a couple of brands that seem to function in every 22 I own, pistol or rifle, so reliability is moot for me now.
If you want to avoid wasting money, no matter which you buy, I'd highly suggest avoiding Remington ammo and Winchester bulk ammo.
For me, accuracy is a wash. Sometimes its nice to feel wood in your hands (insert joke here), so the nod would go to the 10/22 in this case.