I have stayed at most Munich hotels over the years. Here's my take:
1) Nicest place to stay - Four Seasons (but pricey). The best rooms are on the top floor where electric shutters can completely block out all light. I loved this place when I was here on business.
2) Hotels in the heart of the city are great for walking around, but don't have the best parking lots - i.e. few spaces and very tight. Of these Le Meridien is very nice but has some seedy stuff closeby (near main station). Kempinski is nice too but only if you get a Deluxe King or Junior Suite. The standard rooms are pretty poor.
3) If you don't mind staying 5-10 minutes away from the city center, the Marriott and Westin Grand are popular. I like the Westin Grand - excellent parking with plenty of wide spaces. The rooms are comfortable with rain shower, Westin heavenly bed, etc. Free internet. Excellent breakfast buffet which is free if you have lounge access. This is where I stayed during my ED.
FYI My other ED hotels were:
Park Hyatt Zurich - great parking in private underground lot
Schloss Fuschlsee - also fantastic parking
Le Meridien Vienna - very cramped parking but the valet was very helpful and let me park the car myself and told me which spots have neighbours who don't drive (i.e. no risk of dings).
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