iMac Retina vs Logic Pro X

Hi,

I recently bought the new iMac, since my 2012 MacBook Pro 13" couldn't handle the CPU load on some of my bigger projects.

The good thing: no CPU load at all. The projects that I couldn't even play on my MPB hardly peak on CPU/HD. So thats cool.

The bad thing: g*ddamn the GUI is lagging/slow/annoying. Zooming is impossible. Pressing solo takes a full second to change (you hear the solo, but you don't see it applied). Opening mixer is slow. Just about everything feels very slow.

Im very inclined on blaming the (2gb) GPU. I've opened the projects Im currently working on on my MPB and whaddaya know? No lag AT ALL. Some CPU overloads but my workflow there is still better, since everything runs smooth

So then I realized my MBP was still running on 10.9. So might Yosemite be the problem? Upgraded my MPB. Still smooth.

Ok, clean install on the iMac. Everything seems fine. But once I open a project (without ANY of the external plug ins installed yet, just the midi and audio), the lagging is still there.

I understand the GPU needs a lot of power to run this Retina display, but if that means that I can not run a big Logic Pro X file....I dunno man. An audio program shouldn't cost that much of the GPU.

Any thoughts on what could be causing it? Should (and if so, how?) I monitor my GPU to see if everything's working properly? Should I wait for an Yosemite and/or Logic update?

Or, am I just in bad luck because of the hardware in my iMac vs Yosemite vs Logic Pro X and should I revert back to Mavericks for the time being?

Specs: iMac i7, 32 gb ram, 500gb SSD. MacBook i7, 16 gb ram, 500gb SSD