Let's see. The 60D...
* Out resolves the 5D, and this is visible in large landscape prints.
* Has wider DR than the 5D.
* Has less high ISO noise than the 5D.
* Has both LiveView focusing and a built in level, both very useful tools for landscapes. (LiveView is huge when you need to check DoF and use hyperfocal focusing.)
* Can use relatively low cost, high IQ wide angle crop glass. For example: to match the $700 Tokina 11-16 f/2.8 on the 60D you will need a $1,700 Canon 16-35L on the 5D.
* Comes new with warranty.
* Shoots faster, has video, uses modern batteries, and can remote trigger flashes. (Not as important for landscapes, but still.)
* Has a better viewfinder.
The 5D was a great camera, and is still a very capable camera. But at the same price as a 60D it's a silly buy. The 60D is better in every respect except one (viewfinder). And that includes sensor, no matter what format fans want to believe.
I've not shot w a 5Dc, but the output from it IS pretty nice and I've thought about picking up one to play with.
However, I've shot LOTS of landscape with the 60D. It's a VERY good camera and I'd recommend it over an ancient 5Dc mostly for the technical and feature improvements. If you're shooting landscape, low ISO is more important than hi and 60D's low ISO performance is one of Canon's better bodies.
goes a long way on a battery charge too.