I believe the Hotrod only works with a PC, while the x-arcade can work with any current system including the DC...I have an x-arcade and it is really great with the exception of the 1 player controls and the 2 player controls being too close together. No problems with responsiveness at all, and it feels arcade quality. I'm probably gonna chop it up and put it back together with a lot more room between the 1 and 2 player controls...
Depending on how an arcade stick is designed, it is pretty easy to mod it in order to make it work with the neo or a supergun. You can even make it compatible with most consoles via sacrificing a regular controller for that system (it is recommended to use a PSX pad and then buy adaptors from PSX to other consoles).
If you just going to use it for the PC, get Hot Rod SE, it uses actual arcade parts where X-arcades are just some piece of crap wanna be buttons and joystick. If multi-console compatibility is important, then get the X-arcade, but if you can build your own, you should just do that instead.
I've been asking this same question in MAME and Arcade message boards and most people that answered me back preffered Hot Rod SE, I used to own an X-arcade Solo, I had a hell of a lot of fun with it, either way you cant go wrong with both, all a matter of personal preference. X-Arcade gives you a 30 day money back guarantee and you get a free console adapter with the purchase of an X-Arcade Solo.
I own an X-arcade solo and I think it is one of my best purchases. I got it for the Dreamcast adapter, my only complaint is that you have to open it up and fix the sensitivity of the joystick before having some fun.
I did that 4 weeks ago, and I haven't had a problem since.