The only difference I see is that the 302 comes with a little bag to hold it, and also has an added quick release base. The quick release base differs from the regular base in that the regular base is a longer arm that mounts directly to the bottom of the GoPro housing with the thumb screw, while the quick release base is a shorter arm with less adjustability but has a flat "clip" mount or whatever it's called on top.
So it's quick release meaning, let's say that you have an adhesive mount on your helmet. You screw the clip thingy to your GoPro housing and then snap it into the mount. Then you decide you want to put your GoPro on the suction cup mount on the side of your car. with the quick release you would just unclip the housing (leaving the screw tightened) and clip it directly into the quick release on the suction cup. Without the quick release, you would unclip the GoPro from your helmet, unscrew the clip thingy from the GoPro housing, and then screw the GoPro housing onto the suction cup mount arm.
So it would save maybe 20-30 seconds overall. But you could also perfectly set up your suction cup mount (and/or adhesive mount, etc.) and then not worry that your GoPro is tilted at the wrong angle when you are trying to quickly loosen/tighten onto the new mount.
Sounds like a good idea and if you are in the market for a suction cup mount I'd say go with the new version, but if you have the older version (I do) I wouldn't feel the need to upgrade.