I've been with both of them. Both are recommended.
Maci is younger and (I think) 19. She is super bubbly and is very enthusiastic. She seems to be up for almost anything and is very playful. She is very encouraging for MSOG if your session hasn't finished.
Tessa is also very nice, is enthusiastic, is about 23, and has a hippy-ish aura about her. She REALLY likes doggy-style. She's quite intelligent and generally fun to be with.
If I had to score them: Maci 8/10, Tessa 7.5/10. Both are really nice girls and I am considering a repeat.
Have fun!