You can ask for an upgrade at the Dolphin when you first make your reservation and it will be noted on your reservation form. I have always had very good luck doing just that. You can ask again about any available upgrades when you check in too.
As for an Epcot view, I would think you would want the East wing, but if you simply ask for an Epcot view when you make your reservation, that should help. Maybe someone else has a better response. My concern was never the view but being closer to the pool area and having a balcony, so we were in the West wing.
Although I have never stayed in POFQ for the same price I would choose the Dolphin because it is a deluxe resort, the transportation options are great, the beds are really nice, the pool is great, I don't know what else to say. I suppose the only downside is that the Dolphin is not a true Disney resort, there is no Magical Express, and they charge for parking now.
Good luck with your choice. I'm sure you'll have a great time either way!