I have no experience with Arduino at all, and I want to build a small robot for a few sensors and speed/direction control. Is there a model that is more useful, but not overkill? It would be nice if I could standardize on one that had broad applicability. Any suggestions - and reasons for your suggestion?
If I was starting out from scratch, and wanting to build a robot, I might think about the Romeo arduino compatible from DFRobot (http://www.dfrobot.com/index.php?route=product/product&filter_name=romeo&product_id=656
), since it is designed for motors, and you can get it with some robot kits. There are various shields that add motor support, but the Romeo has male pins for adding sensors directly, 2 motor ports, and an external power connection for adding multiple servos.
If you are the type that might fry your board, you might think about the Ruggedunio which is better because it better protected against high voltages (http://ruggedcircuits.com/html/ruggeduino.html