If you don't mind me asking; Surely it would make sense to take the allowance and rent a place where you have control of where you stay and how long you stay as opposed to taking the supplied accommodation and risk being placed in a bad apartment in a less popular part of town for the period of your contract where you cannot move out unless you buy? From what I can see on sites like dubizzle.com etc... one can get a decent 2 bedroom apartment in a good part of town within the housing allowance that is provided of 14325 AED/month. Am I missing something?
It very much depends on the individual since if you are happy where the company has put you, then many (including myself) can't justify to simply move for the sake of moving and moving is a pain in Dubai! If the company was to move you then there is still the option to take the allowance and move to somewhere you would prefer.
When I joined you could change your mind shortly after you arrived and opt out, if you found your company accommodation was not to your liking, thereby keeping your options open but I am not sure if this is still the case? Worth checking before you make up your mind. If you can't do this then opting out is the only way to give you some control over ending up in a place you like.