I'll "broaden" the discussion a little bit. I have a transom mounted ladder on my E32-3. I wouldn't change it.
It depends on what your intended use is.
I keep my boat on a mooring buoy year-round. On average I row out to it twice a week. The ladder is my only way of boarding the boat. I like approaching from the stern, where I can grab a stern cleat or the ladder itself to pull up to the boat. When lowered, the ladder sits in the bottom of the dinghy, probably 2in below waterline. This greatly stabilizes the dinghy as I'm getting in and out. I can walk down the ladder with one hand on the stern railing, a 40 lb generator in the other hand, then step into a stable dinghy, place the generator on the seat, and then seat myself in the dinghy.
Whether this would work so well from a mid-mounted ladder I don't know. I've never used one, but it looks like the mid-mounted ladder might block access to the normal entry gate while at the dock. Am I wrong?
As for boarding-at-sea during swells, obviously the above comments are correct. A Stern mounted ladder would be very difficult to use in rough seas. The question is how often are you going to have to do that versus other intended uses. Me, hopefully never, but I board from the ladder in smooth seas a hundred+ times a year.
In a real at-sea MOB situation, a ladder might not be the answer at all--especially for an injured or unconscious person.