Sprint's Palm Treo 755p or Sprint's new Mogul

Ok...so I've been a huge fan of Samsung's flip phones since the very first time I had a cell phone. I am in desperate need of a new phone, and I thought to myself, "What better time to get a brand spankin' new PDA since I'll be starting nursing school on August 20th?!" My problem is that I am EXTREMELY IGNORANT when it comes down to smartphones/PDA's. From the forums, I've been reading that most of the software that can be downloaded onto a PDA needs to be done on a Palm OS compatible phone. The Treo 755 is palm os compatible. The Mogul--which is the one I REALLY want is windows mobile compatible. I don't know what to do, and I would LOVE for someone to give me more information on this. Is it that there aren't any applications to download at all for Windows Mobile, or are they more expensive? ANY INFORMATION WILL BE GREATLY APPRECIATED!