I know a lot of players who said Rotor is the one but after giving the Spire a try they stick with Spire. Someone already mentioned the field stripping. I would say stripping the Spire is way faster than Rotor. I know the plastic looks a bit more fragile on Spire but after one year of use I still don't have any scratches on it (I'm a snake player). The only thing is that some paint residue has left the black plastic a bit greyish. It was a bad load of balls anyways.
At first, I was afraid of breaking the speed feed, it looks like cheap plastic, Rotor has those rubber ones. The plastics will break if you bend them backwards too much, the rubber ones won't but they tend to wear off over time. I've seen more Rotor speed feeds with missing flaps than any of Spire's. Nonetheless, I'm always very careful around the flaps.
The only time I had a jam was an odd ball. It would have jammed any hopper. Then again, the worst ball we usually use is GI sports 3 stars.
For me it's definitely Virtue Spire