I'm trying to determine whether I should use the *~er* suffix or the *~or* suffix for a person who improvises. What I've learned on the web is that technically one should say "improvisor". The *~or* suffix is for words of Latin origin, and apparently the word "improvisation" derives from the Latin *improvidus*.

However, "improviser" seems to be [the more common of the two](http://books.google.com/ngrams/graph?content=improvisor,%20improviser&year_start=1970&year_end=2012&corpus=0&smoothing=3), and I have to admit, it *feels* more natural to me.

I've been using both, but I want to be consistent and settle on one. 

Which one should I commit to using, and why?