Sure, there are other guide companies working in Akihabara, including Akibanana. But, do you want to walk around behind some guy with no chin wearing fake yellow hair in a cheap cosplay outfit, or would you rather be seen with a pretty maid? Yeah, thought so.
I haven't tried using these companies yet, so I'm not going to try to review them. If you have taken a maid tour, please add a comment here.
Maid Club (Souvenirs)