Do you know the benefits and drawbacks between implementing passenger on the top of Apache and Nginx?
Nginx is slimmer than Apache and delivers static pages a little faster. However, you do not have exactly the same market size that Apache has, therefore you'll find less people who know Nginx.
Apache is much more resource intensive than Nginx, however, you cash better module support than Nginx. Nginx does not have dynamically loadable modules like Apache. You need to compile them in, so upgrading Nginx might be a hassle if you do not keep the source files around.
So far as Passenger goes, they're virtually equivalent on either.