Physical sensation depends on how long its been, how turned on I am and how long we have messed around prior to release. All are awesome but here is a break down....
Low intensity - My taint tingles and I get a feeling similar to holding in a good piss, I feel a little 'pressure' building and my dick gets more sensitive and feels like its swelling then the nerve endings take off on the tip and underside and I feel every friction sensation as it moves in and out (or tongue if its oral) all that builds and then it peaks and out it goes.
Medium intensity - Feels are the same as above, but my whole dick tingles I get a feeling of sensation tingles at the base of my spine, lower back as it builds then lets go.
High Intensity - All of the above, but I actually get the sensations all up my spine, the back of my neck and down my legs to my toes. This is a full body orgasm I guess.... but I can actually feel the load building and gathering, the pressure sensation around the taint and nuts and into my prostate is pretty intense (no pain at all just similar having it milked during a good BJ). When that one lets go I can feel the full load coming all the way from my nuts and a feeling I can only call a pressure wash flush as I cum.
The low intensity ones are more common and feel great.. the medium even better and I need a few moments until I am ready to pull out. The high intensity I will linger, continuing slow thrusts and shivering as I come down off that high. These happen often but not as often as I would like
I usually need a good 5 mins or so until I am back on earth with these but they do leave me drained sexually.. I rarely am able to go again after one of these where I can get 2 out of the others in a 2-3hr session.