I have the Briggs on my Citation and I've had no problems. If I was buying a new one I would spring for the Kawasaki engine. But the briggs on the Citation is fine. The Cobalt might look good on your yard! The larger tires, speed, torque, height adj. etc. are nicer on the Citation so I agree with you on that.
To be honest I don't clean the deck all the time. I either jack the front end or drive on a little slope and usually reach under with a broad nail puller with a 90 degree bend or some other tool and give it a quick scrape down. After initially using the z turn without the mulch kit I didn't like the trail of grass left behind or being covered in dust and grass as it does blow out the clippings. The mulch kit took care of all of that. If money was no object I think I would look at a front mount z turn like a Grasshopper etc. with front mount lift up deck. Would make maintenance a breeze. I do like my Simplicity dealer and try to support him as much as possible with service and other purchases like the Echo products he carries.
I would be interested in engine29's feedback on the 61" vs 52" deck on the Citation with the same engines. The engine on these Citations are a little larger than what came with mine at the time, so that may be the difference. I assume the torque put out by the newer model Citation's would run the 61" without bogging down. That would be my concern with the 61" deck and the heavy grass as you describe. One thing with the z and mulch kit is to keep up with the mowing. "Hogging" of the lawn not recommended. Or if it gets away from me I just mow the tall areas twice taking a little off each time. But that is doesn't happen too often.
engine29, Would the Kawasaki engine have more torque than the Briggs? All of the other info you gave seemed spot on as it should considering your background. I did't mean incentive on the Citation, I meant financing options from Simplicity.
Vic, Your statements on why you want the z turn...I couldn't agree with more. Sounds same as my situation and yard. The Z cut my time by more than half and other than a ditch, eliminated all push mowing for trimming, just a weed whip.