I know it's famous now, but the Merrion for me is a badly designed refurbishment - good on the details, like ceiling mouldings - but awful spa, second basement restaurant and bathrooms. Shabby. Not crazy about the Gilbaud restaurant either - pretentious.
The Clarence is looking tired, I agree, and we're waiting for a refurbishment. Even then though, it's a hotel for pop groups and wealthy thirty-somethings.
Four Seasons is a hike in Ballsbridge, but well worth it. The hotel car gets you into town in 10 minutes or less during the day and it's nice to come back to all that civilised Four Seasons stuff, like great beds and service. No contest.