Have not used a Spire yet but alot of people rate them very highly.......but i love my Rotor, never breaks a ball, very rarely jams, hella battery life and i can throw it all about the place and it just keeps going
I am personally going to go for rotor as my first hopper - there is a lot of support for both so I will go for this first, I am sure I wont be disappointed from what people have said. May eventually try a spire out in the near future to see if there is a lot of difference between the two.
I've heard great things about both the Rotor and Spire.
The Rotor is very easy maintain and slightly cheaper, whereas the Spire is lighter and can hold slightly more balls.
As others have said, it's all down to personal preference really.