There are several threads on Munich properties. Here is one of them.
http://flyertalk.com/forum/showthrea...ghlight=munich

But go ahead and do a search by putting in Munich. Sure you will find more.

Location wise, CY is best as you have figured out.
The Ren has no CL, and it will provide free breakfast for plats in the ground level restaurant. Breakfast buffet was quite good. They didn't give me actual coupon as such. When you check-in at breakfast, they ask for your room # and check you off.

The Ren location is not bad, as the metro station is 2 minutes away.

Have not stayed at the Marriott Munich, hence no Comments about it.