A run down of the Marriott Bonvoy hotels I know of:
1) W - it's great but I would personally stay away because it's a fav for drug parties. The head of security there is infamous for blocking ambulances personnel at the front door to save an unconscious girl in her room citing "guest privacy" (turns out it was drug overdose and hotel needed time to "clean up" before letting anybody up), that tells you about the "background" of the hotel. I've once gotten a suite that smell really bad and I would suspect the previous guests had a wild drug party, but W was fully booked (they claimed) and couldn't change my room, not even a downgrade, and they ended up putting 3 air-filter machines in my room to try to rid of the stink, which didn't work. Never again.
2) Le Meridien - great staff and location and great services. If you have the cash, this is the one to stay at in Taipei in my humble opinion. Right in the middle of the best commercial Xinyi district in Taipei.
3) Courtyard Nangang - sorry, not my thing at all. Way out there in the middle of nowhere (literally nothing to do at night). You can ride the subway to Taipei City Hall which is a few stops away, but anything beyond that the travel time adds up and it becomes a hassle. Simply too out of the way for my liking and again, gets depressing at night.
4) Marriott - great hotel but again too far out of the way, and worst than Nangang. Not close to anything and the Brown line is a bore. Going to Xinyi or Ximending or other places requires a decent amount of time by subway or taxi. Again, depresses by nightfall. Great hotel, horrific location.
5) Sheraton - probably the best in my opinion. Short subway rides to Ximending or Xinyi. Plenty to do around, 5 minutes away from Taipei Main (Train) Station. Plenty of shops and restaurants around the hotel day or night. Ever since Westin is closed this is my go to hotel.