I'd buy the round bales if you can store them, most of the time they're far cheaper in the long run and last longer if you just section it out and throw it to them. I use the same hay from the same farmer as I have been for the past 4 years so I know the hay and how heavy it generally is, with that information I got a rubbermaid tote and figured that I can cram 10lbs of hay in it (I weighed it), so I just fill up that tote twice a day per horse and I'm good to go as if I had bought square bales.
Saves me hundreds of $$ a year.
And yes, horses need fed AT LEAST twice a day, once every 12 hours, or else it is horrible on their stomachs and digestion tracks. 3-4 times a day is healthier, but twice a day has never caused me problems and is pretty common practice.