Its worth doing, I have done both there are benefits and disadvantages to both.
Updating....
Magic/Wonder
The hosts (two) are assigned a side of the ship and call on you during the day.
They take over a bar for the embarkation meet and a party mid cruise, sometimes two on longer cruises.
You get a food gift each day, like a fruit bowl, and the hosts will organise what you need like guest services, so character meets tickets and extra palo.
Often they call on you in the MDRs to give advice on the next day, the plans the ships docking times the weather.
They have been giving out extras these are not advertised but include.
Pre dinner drinks in a bar.
Coffee in Cove Cafe all cruise flash the card and no fee for the standard coffees and teas there.
Priority embarkation, priority tendering where they tender and priority disembarkation at the cruise end.
We have had extra gifts including a create of bottled water.
Personalised service tailored to you.
I am on the Magic in concierge in ten days and will post the up to date service on my blog at that time.
Rumour, Magic may get a concierge lounge on next re fit.
Dream/Fantasy
Concierge lounge.
Three hosts.
You go to them.
Food 7am to 10pm and soft drinks all the tiem and a bar pre dinner.