Honestly for most league bowlers symmetrical balls are probably going to be the best bet in the long run because symmetric balls are more forgiving if your release is inconsistent. Asyms allow better fine tuning with your drilling options though. Also on paper all other things being equal asymmetrical balls tend to show a more defined, angular motion. These balls can create more area at the break point and will respond to friction faster at the break point than symmetrical balls but again many other variables are as important (stolen from bowlingball.com because I am lazy) like ball surface, your style etc. Most of the really strong oilers are going to be asyms. A very strong skid flip asym pearl is often another asym ball people will have in their arsenals (for getting carry on very deep angles). In general you have to see what works for you but most mortal bowlers are going to be better off having at least as many if not more of their arsenal symmetric balls especially if they bowl mostly on house shot imo. That said low rev speed dominant bowlers on here swear by and often need the help from asyms so have to see what works for your style or even bettter get a trusted PSO to help reduce the trial and error.
