Hi Tech,
While I'm sure there are surge devices that are good, there are none that meet my particular needs. The low voltage cut outs are too low for my peace of mind.
Right now I have neither a surge device nor an autoformer. If I were going to get something, the autoformer would be more useful to me.
Folks who have 50 amp service should use the best they can afford. For myself, on my 30 amp service, I'll continue to manually check before I plug in the RV.