The lines for HWE really vary depending on the time of year [off season vs peak season]. We have waited only 15 mins or up to 45 mins. if I could only do one HP park, it would probably be Diagon Ally (DA)...especially if you are not doing rides. DA has the Weasly Joke shop, Olivanders, quidditch shop, magical menagerie, Gringotts bank where you can talk to the goblins, Leaky Cauldron, the Hoping Por [for butter beer], more stores, knockturn Ally , madam malkins, nightbus [right outside the entrance to DA.
Over in Hogsmeand they have Honeydukes, a shop with books and souvineers [I forget the name] and Three Broomsticks. It has less shops and things to see. I am probably forgetting a few things here....
The HWE is a really cool ride. It is liek really being in teh HP world....
have fun!