Whatever you get, just make sure that the soles are thin and designed for riding. Leather soles are ideal because they will slip out of the stirrup easily and you likely wouldn't get hung up even in a fall. Run far away from those treaded soles that look like hiking boots or sneakers.
These are the boots that I wear. They are the only ones I've ever found that were comfortable for me to walk/stand in. Also, even though the soles are rubberized, they are harder rubber designed for riding and they slip out of the stirrup almost as easily as a leather sole (and they don't slip and slide around walking on grass
). Amazon.com: Ariat Women's Quickdraw Boot: Shoes
Oh, and if you have wide feet like me, a square toe will be a lifesaver.