I have had a lot of expieriance with both types of robot builds and have found many differences between the two. As far as coding goes there isn’t much that is similar. Vex gets a little more in depth by using text based code instead of blocks that ev3 uses. Personally if your starting to code robots then you should play with ev3 coders because they give you the basics. Once you feel comfortable with coding robots and you know how to get things to work a certain way, then you should move to vex coding. And also if you can do other text based coding such as java script then you should be comfortable with vex coding. Then there is building which is where most of the differences lie. If you look at the two robots side by side you can see obvious differences. First of all ev3 is made entirely out of legos and vex is made of metal. Also vex has a significantly more motor ports. Then again it is a lot harder to build(even though it is stronger) because you have to tighten screws instead of clicking two pieces together. Then ev3 has an intractable mind, unlike vex which has a lot of ports covering the entire thing. I personally like how ev3 allows you to interact with the mind and tell it what code to run. But it is easier to use a remote control on vex because it has a really nice to use controller. Overall if your a new person to robots you should start with ev3 and if your more expierienced then you should go straight to vex.