You know, location/convenience used to be our main priority. We live fairly close to WDW and go for several short visits per year. We used to try and choose a resort based on which park/s we thought we'd be going to. Unfortunately, my kid has a habit of changing his mind at the last minute so that hasn't worked out for us as well as we hoped.
After location, we look at theme. And for me, that includes the room decor as much as the resort itself. So, for example, when we wanted to stay in the Epcot area, the YC probably has the most appealing overall theme to me, but I loved the look of the BWI rooms, so we stayed BWI.
Finally, but most important, price. We're FL residents and AP holders, so I only book with a discount. We might be totally set on a certain resort, but if no rooms are available with the discounts I have, I won't book it.