I have both of these setups, and both work well, but I've been having problems with the Quark cutting out. I still haven't figured it out yet. I actually have 3 Quarks, and 2 Quarks have had this problem. I haven't tried the 3rd one yet.

The problem I'm having with my Sidewinder is that I'm having problems programming it with my radio. I'm currently using the stock Associated RC18t radio, until my Novak XXL receiver comes in. Then, I'll try programming with that and my MX-3 transmitter. But without the programming, it's working really well. Very smooth and no cogging.

If I were to choose between the two, I'd get the Sidewinder, especially since Sky & Technology isn't around to support the Quark.