I think the bigger benefit is that the 50A socket gets used (and abused) less, so will make better contact then the 30A one may...
A 30A circuit is designed to be used to 24A (80% of rated OCP) - A 50A circuit will have more available power; so if you're pushing the 30A to it's max, there may be an advantage to using the 50A.
Last thought - 30A trailers are more common, so depending on how the posts are wired, there may be more load on the 30A "side" of things, which could lead to less stable power - but that's very much dependent on how the park and post are wired.
2014 Grey Wolf 28BH, behind a 2015 F350 Diesel Crew Cab
Nights Camped 2015: 37
Nights Booked 2016: 44
Nights Camped 2016: 41