Look at the "technology" section of the Starboard website.
That will hopefully explain the differences.
I have the regular Rio M (not ArmoutTech or Sport) and the boards have been very durable for me.
If you are in the USA, I think you will only be able to find the basic Rio, but I could be wrong.
Get the regular Rio and I think it will serve you quite well.
The Rio Sport is lighter I believe and the ArmourTech is heavier.