The best comparison I can bring is with BA's Concorde Room at T5, after four years as a CCR card holder.
Bearing in mind that the CCR is an exclusive F lounge, I can still say for the record (though based on a single visit to the Suite), there are two, and only two things on which the CCR scores over the AC Suite: a view of the apron, and the champagne (LP Grand Siècle). On every other point of comparison, the Suite beats the CCR.
Access: CCR is open to any type of F passenger: paid, upgrade, reward. Also non-F passengers connecting from any type of F. And it is also open to a group of cardholders so small that our positive space reward entitlements are managed on an excel spreadsheet. All of these people also have guest privileges with that, and that burns out the space pretty quickly. I have never seen the CCR less than full, and often heaving.
Facilities: Yes CCR has showers (outside) and a spa (good luck getting a treatment) and cabanas (well, cells). But the only time I ever use any of these are the showers after getting off the TATL and connecting elsewhere. Since it's my connecting BP that determines my priority for a shower, the intervention of AC Concierges for the MLL facilities is likely to result in a better experience.
Service: This one's pretty subjective, of course. But experience with service in the CCR vary from "indifferent" to "glacial". Without a buffet or any kind of self-service, you're left to waving your arms until someone takes pity on you to bring you a glass. There is table service dining, which is generally fair. The food isn't much to write home about. In the Suite, the service was somewhat wooden, but it was prompt and responsive. The food was as good as any food I've had in any F airline lounge (certainly better than the QF F lounge at LAX, which is the high bar for North American based facilities).
Ambiance: The furniture in the CCR was definitely showing its age until a recent refurb. But new upholstery can't do anything about the noise on the terrace (by far the best place to sit--if you can find a seat), or the somewhat cramped clubbiness of the peculiar mixture of sofas. The Suite has the advantage of being new, of course. But it also has the advantage of less wear and tear on its fabric.
There are a not inconsiderable number of F and GGL pax who simply stop in the First (aka OWEmerald) lounge after clearing security in the First Wing (which *is* the best ground experience that any airline has ever designed, IMO). Some even head to the club lounges at T5 North or T5B and forego the "First" experience.
I, for one, think AC have it right here. The lounge experience is a transactional one--you are waiting to board a particular flight--not one flight out of the hundreds that you have ever and will ever take. The only change that I would encourage AC to look at is to permit an eligible passenger to bring one companion who is flying in J on points or an upgrade. I often use points or upgrades as a way to bring my partner on a trip, and it would be nice to both have access to the Suite if I'm paying cash for my seat up front.