They are not all the same as far as their offerings. Service level-wise, it is nice to have. Too, considering the hotel differences, you also experience a slightly different type of stay at each. For example, there's technically two types at the Contemporary (12th/14th floors) but the food is now the same for both. The GF has rooms that you can pick from three different views and in the main building, only concierge guests can get to that level.
That's pretty much a function of most concierge levels; only the assigned guests can get to that alloted areas. Food quality and quantity varies. Prices too. Most would say the extra cost is not worth it. Until you really try it once, you can't really answer whether it's worth the price for you I would say though.
Oh, did I forget to mention the Poly:animwink:? This is our concierge of choice. Yes, we pay for it. You get your own building, a very nice lounge, great views and more food that you can comfortably eat. Especially on the nites they bring stuff from Ohana's. And the staff, many who have been there for a while (and after several visits on our part), know us on sight in some cases. You cannot beat the staff at Hawaii. We always go at Xmas so the extra ambience of decorations and Poly's unique Christmas music make it THE place for us to relax. In the last ten years, we have never had a bad stay at the Poly concierge.