Well, the bigger connector is what you needed to use (with an adapter most likely) to connect to your new head-unit. The little one is the secondary (windshield or fender?) antenna in the dual-diversity system which probably is useless to your JVC. If you can put the plug back on your antenna lead without rendering it useless, you will then probably need an adapter that looks like this:
It's typically available to adapt to VW products so it should be readily available. If you've ruined your rear antenna cable, I have no advice for you but check here:
Real OEM to see the diversity antenna wiring (part #5 for your car) from the rear-glass-antenna amplifier. It looks like the diversity system for your car used a rear-windscreen imbedded antenna along with maybe a short-stalk fender-mount. I don't see any ti listing for a front windscreen antenna. Why don't you tell us what your car has for antennae?
-Phil