Both of those seem to be popular radios. The JR XS3 is a lot nicer radio than the MX-3 since it can mix channels and doesn't require any crystals. I'd say JR's XR3i is more along the lines of the MX-3 though. If you decided on a JR, they all come with the Z590M high torque steering servo and they have 85 ounces of torque at 6 volts. I just looked up the Airtronics servo and it has 50 ounces of torque and is a tiny bit slower. Also, the JR servo has metal gears while I think the Airtronics has plastic gears. The MX-3 is the cheapest of the 3 at a little over $100. I saw the XR3i at the hobby shop for $170 and the XS3 was a little over $200. Since you want handling, when comparing the Airtronics servo to JR's servo, the JR has a better servo. But, it's going to cost a little more than the MX-3. The XS3 is the most expensive, but it would be the best if you're going to ever run at a track with a bunch of people since you can use any frequency. You wouldn't have to worry about not getting to run because some other guy is on the same channel and you don't have any extra crystals.
I just bash around in parking lots with friends too and I have the XR2i. It's just the basic 2 channel AM radio and works great for what I do. The XR2i AM cost me $100, which is just a tad cheaper than the MX-3 FM, but I still got the AM radio because I'm a poor college kid and I wanted the better servo. When I get my Savage SS, I'll either be getting the XR3i or the XS3, if I want to spend the extra cash.
