The definition of BEST depends heavily on your expectations and needs. If your objective is the best interest rates, more or less all banks offer similar rates and there is not many differences between varioaus banks in Dubai.
If you are looking for easy loans or customer services, thats a different thing.
My advice would be to go for the bank which has a branch closest to you; either your apartment or workplace. Also locate the ATM's nearby so that you won't loose money in terms of services charges.
Hope this helps