Speed alive:
The popular bases are certainly Ireland and the UK (home bases for a large amount of pilots) aswell as the German/Dutch/Belgian bases (again home bases for alot of people). Also the sunnier places such as Malaga and Faro are popular. Think the canaries bases are somewhere in the middle due to their remoteness.
The less popular bases would be the eastern european and morroccan aswell as the far flung Italian and Greek and maybe some of the Spanish bases also.
However, unless perhaps you're coming as a DEC on the condition of getting a certain base, the whole thing generally tends to be a lottery - and unfortunately I would have to say that the general policy seems to be to NOT give pilots their preferred bases. Some get lucky but it generally takes an unreasonable amount of time to get a requested home base and you can expect to see new joiners get sent to your requested base long after you applied. This is in fact one of if not the biggest reason(s) that people get pissed off and leave.
Of course you could be one of the very few lucky ones who happen to get their base of choice quickly, but it's unlikely.