That might be related somehow to the steering lag that exists in RBR? Check this: http://torttu.net/temp/rbr/steering_lag_fix.txt
I think I have only one default car left in RBR (but even that's with new model and skin) but for a beginner I would recommend sticking with the default cars for a while. Though I recommend getting new updated models and skins for the default cars, without changing physics because the original models and skins are really low-res and look like crap anyway (good that devs concentrated on physics instead of accurate car models, because modders would do it with better results anyway ).
I'm not any physics expert but I would claim that the default cars handles the best (especially Subaru '03 and Peugeot 206 - not surprising that those are the cars that Richard Burns had driven?). All respect to Rueda & co. (Rueda is "RBR physics expert") but I think most of the mod cars handle too easy, this problem is especially with the historic cars, which is of course logical because RBR physics engine is made for WRC cars and have some real problems with fiddling the physics (mostly engine and differentials, afaik you can't make diffs disappear totally from the physics which would be needed for historic cars). That's why the Group B Mod is currently postponed. Though the Lancia S4 beta handles great with the 450/550 hp physics, probably far from 100% accurate handling but at least it handles totally different than the WRC cars. You can really forget pushing full throttle.