Lots of things to consider, without even getting into the dolly vs flat tow.

Answering your question 1st, in my opinion, surge means the toad actually has to continue going forward, pushing you before it applies braking. That makes me lean towards electric brakes. Again just my opinion.

Other considerations:

1. Your toads ground clearance and how the dolly will accommodate loading.  Some  require extension ramps, etc.

2. Do the dolly wheels pivot? We had a dolly that the wheels were fixed and it went through tires rather quickly. 

3. Can your toad tow the dolly so you can move it to a remote parking lot if the campground won't allow it on your site?

One thing I strongly recommend is you always carry a spare set of tire straps. You might be amazed by what potholes can do to knock a strap free.