Most the time, if given a choice, I would take a manual over an auto. A watch can never be too thin or light for me, so I'm happy to be without a rotor, and I also like the greater stillness a manual has. A couple of autos I've had have had thin casebacks, and the rotor has been very audible. I also simply enjoy being obliged to wind the watch each day: the auto winding brings me no benefit (I would change my tune if I had a screw-down crown, I know)
At the moment most watch companies are generally wary of producing manuals in any genre other than dressy, and so choice is limited if you're looking specifically at manuals. I end up daydreaming about watches that will never exist.
If I had the chance to turn one auto into a manual, it would probably be the entry level daily wearer style Grand Seiko, the SBGR053.
It's only 37mm in diameter, but thanks to the 9S auto movements being 6mm, it's 13mm thick.
(I would also appreciate Junghans putting the 2801 into the 38mm Max Bill as well as the 34mm model)