We have sailed many times on different lines, but we do prefer Holland. Recently, it has been necessary for me to book an accessible cabin for mobility issues. Once again Holland rises over other lines, as they frequently can/will accommodate wheelchairs and scooters in tender ports whereas on Princess, for example, I'm shipbound unless we're docked. This last adventure was almost perfect; in fact ship's staff called us twice before the first tender port to make arrangements to help me disembark.
I would say our cabin was great but it had a serious flaw for an accessible stateroom. Cabin 6004, a veranda on the Westerdam, is apparently the only accessible cabin with a verandah that will sleep 3, which we need. However there is a massive structural post smack inside the cabin door, making it almost impossible to maneuver once inside the room. The bathroom does offer a roll-in shower but the accessibility stops there, as there is neither a raised toilet or an accessible sink. Bottom line: DO NOT BOOK CABIN 6004 ON HOLLAND AMERICA WESTERDAM if you are actually disabled!
On other notes, Westerdam is scheduled for dry dock in April 2017; try to avoid her until then, she needs the refurbishment. The staff, as always on HAL is amazingly gracious. These dedicated people work so hard and yet they are always so lovely. The food has been better on other voyages, but we learned quickly to take our waiter's advice and meals improved immediately.