Think hard about it
WAAS is nice. I had a non-WAAS 430 in my Warrior before buying my RV, which has a 430W. Now I can fly coupled LPVs and my autopilot can also fly holds. And the refresh rate of the screen is faster, which is helpful when you?re using the 430 GPS as additional info on ILS and VOR approaches.
BUT: in the grand scheme of things, given the kind of flying I do, WAAS just doesn?t matter much. If I had a non-WAAS 430 and $4,000, I?d keep the old 430 and spend the money on something else. Autopilot, flight instruction, better engine monitor, etc. Just an opinion.