Think of surge protection or an EMS like insurance policies on something. Do you want insurance for just part of your investment or for everything?
A surge arrestor will protect your electrical system from voltage surges and spikes but that is not the only thing that can harm your electrical system. Pedestals can be miswired, have floating neutrals and bad grounds, some yoyo may change a connection upstream of the pedestal with disasterous results (I've had that happen where I live; fortunately, I caught it in time), voltage can run low which will eventually destroy appliances, A/C, convertors, electronics, etc. or run high which will destroy them even faster. Frequency can be off (that is more likely to happen when using a generator). An Energy Management System (EMS) will protect your electrical system from pretty much everything except a direct lightning strike (only God can protect you from something like that).
An EMS, such as the Progressive Industries units or the Surge Guard unit linked above, may seem expensive but add up the cost of replacing your TVs, computers, convertor, refrigerator, microwave, etc. and see how it compares to the cost of an EMS. You just might think the EMS is a bargain.
There are basically two kinds of EMS units available: portable and hardwired. Portable units are far easier to install (just plug them in) but are subject to possible theft, possible weather damage (unlikely but still a possibility), and you have to go to the trouble of hooking them up everytime you set up and remember to take them with you when you tear down.
A hard wired EMS is out of sight and out of mind. No hooking up, no worries about waether or theft, no remembering to take it with you when tearing down. An additional advantage is one can install a remote monitor inside the RV so you can see at a glance what is going on with your electrical supply.
I recommend the Progressive Industries units
. Based on reports I've seen on various RV forums, the PI units have a better warranty backed by far better customer service from the manufacturer. The hardwired units use modular construction so if a board goes bad, one can swap it out instead of having to ship it back to the factory for repair. This halves the downtime of the unit. The techs at Progressive will walk owners though the necessary diagnostics over the phone.