I was wondering, what peoples opinions are on the harmonica with square holes and those with circle holes.

Do you find a difference in playing them? If so what?
Or do you find there is no difference?
Preferences? etc.....

round holes are a bit more forgiving of technique, square holes are slightly less restricting of air flow. I assume you're talking about chromatics.

Yes chromatics. In your opinion, what is easier to play? Or does it just depend on the style/genre that you are playing?

Not quite sure here...
I don't know if it's a proven thing but going my "instinct", I'd like to think round holes are better, just consider that Nothing is square about Your mouth; Your mouth corners are round, I'm not sure if Your tongue is round but it's definitely Not square, so I would imagine it's easier and more secure to play round holes and using tongue-blocking...
I have Both types of chromatic, a Hohner Chrometta 12 with square holes, and a Suzuki SCT-128 with round holes, and I personally find that playing on round holes feels a lot more natural and pleasant when playing.
I have No idea whether this is a "proven Theory", just my opinion...

Chromettas aren't really equal to a square hole harp, more like a square hole garbage pail. Not that I don't love the tone. For a pucker player the round holes give you a bit more isolation from the adjacent holes. For a tongue blocker or switcher I'd prefer a normal square hole harp.