Take a look at the specs of each unit, and look at over/under cutout ratings, and joule's too.
We have the older Hughes RV450 model, and the TRC 50A Surge Protector. The Hughes cost much more. And more important to me, the newer 50Amp model is not as robust as this older unit, so it would be hard to replace.
For this reason I put the Surge Protector inline in front of the Hughes. My thoughts were I did not want to be on a power line that was low enough it would trip the TRC, and yet I still get the Hughes Autoformer to cover lower power above the trip point.
LOL! About two years ago, a pretty good thread on RV.Net, where I had my ability to tie my shoes challenged quite a bit... Still feel I'm doing things the right way, for me... My money, so I do this my way:)!
You will find quite a bit of good info if you do a search and find this and other threads on Hughes Autoformer...
So far I've had my Surge Protector protect me twice. Once for low power (moved to a different site, it was that pole), second time for just a very poor wire job for the full park. Finally found a 20amp service that was not too dangerous to hook up on...
Best of luck on your decision, be safe, and have fun,
Smitty