While it is interesting to know what other people have as their tender, it is more important to ask the reasons for their choice. Think about how you are going to use it - frequency, number of people, speed, distance etc. For example if it is infrequent use then the smallest most basic one may be adequate. increased size means greater weight, bulk and cost which brings up handling issues - lifting on the boat, storage etc.
On my old 37 I had a 2.4m which was OK for 3 people and we usually lifted it with the spinnaker halyard onto the foredeck where it just fitted. No space for stowage in a locker as on a 3 cabin boat the cockpit lockers are too small so I built a teak grid platform just in front of the hatch for stowage, deflated for longer passages. Most of our dinghy use was short runs ashore so did not bother with an outboard. On my current 33 I have a 3D 2.4m roundtail as I only use it a few times a year and it deflates easily and stows in the locker. Easy to handle as it only weighs 14kgs.
Size around 2.4m is the most popular as it is the best compromise for most people, but clearly if you want to carry larger payloads longer distances then a larger dinghy is better, but more difficult to handle and stow. In a way the size of your boat is relatively unimportant as in the range 33 to say 38 the problems of handling and stowage are much the same. Above that size stowage on deck becomes easier or the possibility of fitting davits comes into play.
