Oh wow, Malta is meant to be beautiful!
My fiance has family in Barbados plus I do know the island pretty well myself so I think we are going to, by and large, do it ourselves with help from his relatives. My feel would be, it depends on what is important to you. For me, it is having the right venue and a gorgeous dress. I don't really care about flowers and table decorations and the like so for me a planner is not massively important- we are probably going for a hotel where they will have an onsite planner. If you are a bride that places a lot of importance on the details (and that is a totally valid wedding choice, bride your own way) then you may well need the support of a planner because otherwise it is going to be a job of work sourcing everything you need.
Why Malta? Any particular connection or just because it looks awesome?