Personally I'd go the RoRo route anytime, generally its a fairly secure way of transporting a vehicle especially if you use one of the big shipping lines that want access to US and European ports - extra security is required at the port of embarkation. Just secure anything of value, ease of picking up in a box.
You can get 20' open top containers, but you always pay a premium as they have to be top loaded - which means they get unloaded at each port of call and then reloaded. Whilst damage is very rare during loading it does increase the risk each time the container is picked up and put down. The other hassle is that in most cases the container has to be taken from the port for unloading and an overheight container can be a cause for all sorts of problems if the country you are entering does not have vehicles suited (anything from needing overhead power supplies shut down to police escorts at your expense).
RoRo ships have fairly regular shipping routes - make the assumption that all routes start in Asia (Japan, China, Korea) and go either East to the West Coast Americas or West to SE Asia, Australasia, India, Africa, Europe and sometimes East coast USA, they then reverse. Most shipping companies will have web maps showing their routes and timetables.
RoRo you get to drive the vehicle from the port.