I used sidepull on my girls to start them. HOWEVER my paint didn't like it, and after I switched them to the bit and tried to go back to sidepull my qh didn't like it either. I used the gentlest possible sidepull (just like a wide leather halter with reins attached - awesome hand-made thing for the price I got on ebay). I tried bosals once, but my horses are not trained to neck-rein so it didn't work for me. Also personally I don't like the pull on nose for either bosal, true sidepull (with the stiff piece on nose), and I absolutely dislike mechanical hackamores. You have to have very soft hands to use the mechanical hack.
Just wondering WHY do you want to go without bit? Any teeth problems or something?