I switched from Rotor to Spire.
I initially found it lighter and quieter, but then I found as I started to play faster the speed feed I was using would not take the paint quick enough, and I was losing at least 20 balls from my pod onto the floor.
I then tested the GI hopper with the built in radar and found it was not very power efficient, the batteries did not last a day.
I have now got another Rotor and now don't understand why I changed!!
It def is personal preference. I used to have a rotor and now have a spire.
The rotor seems to just be so much more simple which I quite like. Also it seems to feed the last few remaining balls some what better then the spire as, as default it has a internal spring loaded ramp.
Spire, being smaller and lighter is a nice advantage! but without the ramp (which can be purchased separately). I find I need to shake and shoot the last few balls. It's not a big issue, and it doesn't always happen. This can be overcome by filling up early or buying the add on ramp.
Juts seems a shame they didnt include this as standard....as otherwise I would say Spire all the way!