In my opinion, all side quests are worth doing, regardless of the amount of experience they bring you.
Side quests give you the opportunity to explore different parts of Wizard101. I personally enjoy doing Colossus Blvd. and Crab Alley, as well as any other side quest I can get my hands on - solely for the experience.
I would encourage you to do all of them regardless, but, ultimately, it is your choice.
