As others have said, it''s much harder to knock down a 34 foot keel boat than a 16 foot centerboard dinghy. And, even if you do manage to get knocked down, it''ll probably pop back upright as soon as the wind pressure is off the sails. There is, as Jeff points out, the possibility of water entering through the companionway or cockpit locker while the boat is on its side, but that is not supposed to happen in a properly designed boat in non freak conditions.
But my main advice to you, worth every nickel you''re paying me for it, is to keep sailing a lot in that 16 foot boat you mention. It''ll teach you more about sailing and boathandling, and teach you much faster, than the 34 foot boat. Practice in heavier and heavier air and bigger and bigger waves, but pick times and circumstances in which you will be safe (such as, larger boats nearby who are aware of what you are doing and who can rescue you if you get in trouble). Bring along a physically strong friend, ideally one who is a good sailor. Get to the point when you can maneuver that boat through tacks and gybes, in gusts and in lulls, on top of waves or in troughs, and keep it flat the whole time.
That''ll give you some satisfaction and confidence in your skills, which, at the end of the day, will make more difference in your safety and comfort than will the boat design.