Haven't stayed in either of these properties so can't recommend one or the other.
Although both are near the English Garden, they are pretty far away from the Alstadt. The Courtyard is better situated for siteseeing. And, if you are going to be there during Oktoberfest, the Courtyard is located between the festival grounds and the Alstadt.
I have stayed at both, many times.
The Ren. has always given me the upgrades to a nice quiet suite. There breakfast is thrown in and is very good.
I do like to go to Champions Lounge at night in the Marriott. The place has good snacks and a lot of nice people.
I just prefer the larger, quieter room at the Ren. You may enjoy the metro close by to get you to Marionplatz. Don't forget The Hofbrau House!
Likewise, go to the "Lecker Bison" (Pictured) hot dog/bratwurst stand! Nothing like it! Near all the food stands on the East end of Marionplatz.
Have a great time!
We just stayed in both hotels in Feb as well as the cortyard.
The Marriott Munich was by far worth spending more points on. We stayed at the Renaissance b/c I had the same question and decided on less points. The renaissance was ok but rooms were not updated. We were upgraded to a suit and it looked like a flordia condo.
The marriott munich we stayed on night in and I wish we stayed our whole trip at. We were again upgraded to a suit with two balconies, mini bar was free and the rooms were updated. Service was great and the sports bar was good.
Both are close to the subway (renaissance one block closer)
We also stayed one night at the cortyard. the coryard is in city center. so, if you are looking to be close. this would be your choice. rooms are nice for a cortyard, resturant was fantastic.
The Marriott was more recently updated and more modern environment. It also has central room air conditioning which is at times an issue in Munich. It also has a lobby cafe which comes in handy to leave the room a bit. The Renaissance is more likely to upgrade you if you are Platinum but the room s are a bit more worn. Both offer free breakfast in Platnum, neither have an Executive Lounge.