In general, the grip goes somewhere. If you equalize weight transfer, you generally maximize handling, since all four tires are carrying the same lateral load. Without it, you're giving one or two tires much more load than they can laterally grip and handling suffers.
Using a sway bar in the rear is a an effective way of neutralizing handling for the street, but if you are going to race this car, I might suggest more negative camber on the front if you can get it. You could run up to 1 or 1.5 degrees on the street if you don't mind a little tire wear, but 3 and 4 degrees is pretty normal for weekend autocrossers. You could experiment with camber in the front until you're more neutral... just make sure you test it in the rain, too.
The grip that you get from camber comes from tire deflection and you won't get enough traction in the rain... hence wildly oscillating handling.