It appears that no one who responded to your question watches much snooker. The top snooker players in the world - and anyone who aspires to be part of that group - shoot ONLY with an open bridge. There are predominantly two reasons for this. One is that a closed bridge restricts your down table vision. And, like virtually every professional snooker player, when you're shooting with your chin on the shaft of your cue on a 12-ft table with small balls, being able to see down table is extremely important. The other reason is that snooker cues have an extremely short taper (18mm to 9mm in about 14 inches). That taper will cause the shaft to bind up a little in a closed bridge on shots with a long follow-through. With regard to using a closed bridge to improve draw shots, I would suggest closely watching a few snooker matches on YouTube. You will be amazed at the strength and precise control that can be accomplished on a draw shot with an open bridge. Nobody in the world does it better than those guys.