Not really. Both work well, allow you to select which apps you want to use over 3G/LTE and are easy to set up.
I bought both a while back and use My3G now. They claim to use a dynamic methods to trick apps were 3G Unrestrictor supposedly uses one and if that doesn't work for a particular app you won't be able to use it outside of wifi.
Personally, I've never run into a situation were 3G Unrestrictor failed so I'm not sure how much stock I'd put into that claim. I do like how My3g has a little icon that slides in from the side of the screen (just for a second or two) and lets you know a particular app is ready to use with 3G/LTE.