The only way I would ever book concierge is if it were a short cruise and I spent my entire cruise in the cabin or concierge lounge.
We are a family of 4 who like to sail frequently (for example, this year alone we will be sailing 4 times. Last year we sailed 5 times etc..) Always in a veranda category 5A (so standard veranda, not family) This is plenty of space for us, although we have been considering going to a 4A sooner or later.
****DISCLAIMER****This is based on MY family and our travel preferences...just like anything else, every family has different needs. Many of the things I list, will not apply to you as a first time cruiser and you may find value in them.
The cost efficiency for us is just not there for the following reasons:
1. I book our excursions, dining, meet and greets, beverage tastings etc. So I do not need concierge to do it for me.
2. We don't want a cabana even though now as platinum we have a better shot at getting them. We actually sometimes do not even get off the ship and if we do, we have lunch, stretch our legs on the island and then get back on to ride Aquaduck as many times as possible consecutively. lol
3. As platinum we are boarding group 1 as with concierge guests. After Family of the Day, but slightly after concierge. Even before we hit platinum last year, we still ended up with BG 2 or 3. It is all about the port arrival time you select when doing online check in that determines your boarding group number.
4. We are not heavy drinkers so "complimentary drinks" (and I am putting that in quotes because in fact one does pay for that in their cruise fare) does not matter. Soda is also available at drink stations and dining room complimentary and I don't mind walking upstairs to deck 11 for snacks or drinks. (we stay on Deck 10 forward) And you can always bring soda onto the ship in a carry on if you like a brand that is not available on the ship. They have Coke products on board though and that is my preference so I lucked out.
5. I have never had trouble with the main dining rooms regarding service or food quality and we dine at Palo once every cruise for dinner (tried brunch and was not overly impressed)
I hope you enjoy your first cruise no matter which type of cabin you choose. They are addictive though...clearly in our case anyway.