I want to have internet service while I travel in my RV. WiFi at the campgrounds or satellite? what's best?

WiFi makes me a bit nervous. Is it secure or how do I make it secure.

Is satellite as good as it may appear to be?

Depends on how secure you really NEED it to be, satellite has a lot of downfalls in cost and latency. Generally I'd just say to stick with wifi, and make sure that security sensitive stuff is done over SSL (websites that begin with "https://" not "http://")

It is common for hackers to lurk around RV camp sites, intent on stealing vacationers sensitive files.

Wifi in public places is fine for email and web browsing provided you run a good firewall and wifi security programs. I would not trust public Wifi you are going to be using it for banking or other sensitive applications. I have also met full-timers that used cellular modems for places where wifi is not available or when they were concerned with the security of public Wifi. I believe that satellite still requires a landline for uploads.