Best for us is the cheapest. If very close to, or cheaper than a normal veranda when desired perks are added, the extra points are nice. We're not on 'Team Blu', so won't pay extra for Aqua because of that.
M-class is the only class where Concierge & Aqua do have larger rooms, so that may be some consideration, but location is not always the best with 'better' rooms. Call a less desirable location an 'upgrade' and people will suddenly want it. Though we love the deck 11 rooms and have booked Aqua solely for location when the price has been minimally above normal veranda.