I think Birch was my personal favorite
But I still like Kikui a lot! They're following the trend of younger and more attractive professors that Juniper started, which is interesting.
PS: DO NOT google "tumblr pokemon professors" at work. You'd think Sycamore's the only one, but no. Oh no. Apparently there isn't a single professor that doesn't fit in with someone's fetish. I just found out the hard way.