One of the aircraft I fly has 2xGTN750 (a C414.) + a Garmin 600 EFIS. Can't say I'm too enamoured of the touchscreen compared to a GNS530. I like the new functions & capabilities but the touchscreen UI is bloody annoying. It's the constantly having to go back to the main menu before being able to select an alternative collection of features that is the worse, but also trying to touch the correct spot in turbulence isn't exactly desirable either. At least with the 530s you can go directly to many features with a dedicated button. Also you have a knob to grip while making inputs. Much better in the bumps. Harder to mis-press a hardware button too.
I don't like that beyond a certain level of zoom the weather is always N. UP, even though I selection TRK UP in the menu.
I like being able to slide the image around the screen, however. Bit odd that they'd have that but not pinch-zoom multi touch functions.
All in all, I'd rather 530W.