I have olympic lifting shoes, and I love them for squats. I have poor ankle mobility coupled with relatively long femurs, so they let my knees come forward further which keeps my back a bit more upright. Other people with different builds may not need them, but they certainly help me.
One thing you can try is squatting with your heels raised under plates or a board. This isn't all that safe, so I wouldn't recommend doing it regularly, but once or twice to see how if you like it is worthwhile before you spend the money on the shoes.
For bench, I don't think it matters much one way or the other.