I would have thought a possible solution would be to request one, but inform the controller that you are able to take the other if it suits them better...
i.e. ...........request VFR entry clearance, can accept IFR clearance if required
.....as you have seen from the replies here, it may depend on traffic situation, weather, level, etc. So what might be good for the traffic in the Class D on one day might not be so good on another day. Giving the controller the choice for what suits them better is always a nice way of doing it!!
If all you state is requesting entry clearance, then yes we will ask which flight rules you can prefer or can accept.