Personally, I have not used the EV3 revision of Mindstorms, but I can tell you from my experience with the Mindstorms NXT 2.0 (the previous version) that Mindstorms will likely be underwhelming. The EV3 brings little to the table that NXT 2.0 didn't offer aside from more sensors and a new motor which doesn't function exactly like the regular servos from the NXT 1 and 2, but probably has far less torque and more speed. More importantly, the hardware, though simple and easy to connect to ordinary LEGO structures, is not nearly as precise as one might expect. If you plan to build path following autonomy into your robots, expect multiple centimeters of inaccuracy in movements and distance readings from the ultrasonic sensor. However, for simple projects, this might not really matter.
Admittedly, my talking points above might turn out to be trivial matters for you as I am unsure exactly how advanced you plan to get with these bots. What I think would be most important for you to know is that you can't just 'program' a Mindstorms kit. You have to use an included software with a tile based system, which as I have known myself, coming from a scripted platform like Arduino to tile-based stuff is extremely limiting. Though it is possible to build considerable complexity into your programs, they will be processed slowly, and you will need to often program in delays or use other tricks to allow information to be processed accurately. When using the tile based system, trying to make a long program with large amounts of complexity will end up looking like a massive mess of connecting lines and wires on your screen, and anybody unfamiliar with the system will have no idea how the program works.
My advice is: if you have been okay using Arduino before, you may like to stick with it. You can use regular LEGOs as a platform to attach traditional hobbyist robotic parts like servos and motors if the ease of construction is all you require, as LEGO itself is a flexible building platform. I was able to construct a remote controlled car with a regular 550 can motor and a hobby servo for steering using LEGOs for the entire chassis and wheels. Just get creative, build a platform for an Arduino, and you have a fully programmable robot on the cheap!
P.S.: The total cost of parts for my car was around $50, though I had some electronics already lying around. Much cheaper than a whole Mindstorms kit to use $10-$20 servos and $5-$10 motors along with a $35 Arduino controller.
