I don't know the exact specs between the two carbs to list off the exact differances. The slides are differant, the way the carb pulls fuel through each jet is differant. the adjustments are differant. PJ's use the choke nob to set idle. there are several things that are differant, but the main reason people get them is they are more simple to tune, and are a more common carb now days.
like I said either carb will do, they just have thier differances, I first had PJ's and sold them for some PWK's. Then I sold the PWK's and went to alky Mikunis, and I just got a set of Lectrons that I am going to try out when I get back to the states.