The handling/physics are notably worse (in my opinion). They feel very wooden, like there's too much grip on all surfaces and just when you're about to slide the wheels just stick on the road like they have glue. I can't describe it better I'm afraid, but I've been playing rally games for many years and it just felt wrong from day one. Dirt rally 1 & 2 felt like a revelation back then in comparison.
Visuals are a sidegrade, worse in some aspects despite how many years it's been. The look of the game is very sterile compared to dirt, for me it's an overall downgrade.
Performance is an absolute mess for a racing game and when I played it was already improved from launch.
The structure of the campaign is really bad, you always have to choose between events and you can only bring a very limited number of cars with you. It feels like they tried their best to suck as much fun out of it as possible. It was a huge disappointment and the final nail in the coffin for me.
We need a new game, preferably dirt rally 3 and they need to bring their old engine and physics model back.
I disagree with everything mentioned here except performance, and visuals (to a lesser extent).
There are certainly performance issues, but far from an "absolute mess." I get the occasional stutter while browsing through menu screens, but that's it. Going on to about 15 months of playing WRC, I've had zero problems with stuttering while driving on a stage to date.
The graphics in certain locations do look a bit better in DiRT Rally 2.0 when compared to WRC. However, the gap has been closed significantly as improvements have been made to stage visuals with patch updates to WRC over the past few months.
If you're having issues with handling/physics in WRC, then you're either driving with bad car setups, or default car setups.
I loved DiRT Rally 2.0 -- especially while doing Daily, Weekly and sometimes Monthly Challenges. But the additional stages, cars, plus other features and options included in WRC make it now an overall much better rally game. Getting through all the Moments in WRC alone make this game much more worthwhile to play over DiRT Rally 2.0 in my opinion.