My advice to people putting in an RV outlet falls into two identical parts:
First part: If having an electrician put it in put in a 50.. Reason.. I have read far too many threads where the RVer hired a pro, even if it was his brother-in-law, to install a 30 amp and the pro wired it for 240 volts and blew all the electronics in the RV.
However they nearly always do the 50 amp right, and the only time I have heard of a 50 amp being done wrong it was in an RV park which did a low-cost upgrade from 30-50 amps on some sites (Did not pull new wire ran same leg to both sides of the 50 amp outlet.. A no-no).
And the other part:
Weather you do it yourself (If qualified) or hire it done.
Put in a 50.. That way,, If you ever wish to upgrade to 50 amps.. Already done.