Well, since I have both, I figure I'll chime in. I use a 12cf chest freezer as a kegerator and my old 19cf refrigerator (w/bottom freezer) as a fermenter. For me, the chest freezer works better as a kegerator since I can put more kegs in it, while using the fridge as a fermenter since I won't be lagering/cold crashing more than 1-2 carboys/kegs at a time.
IMO the pros of a chest freezer are: cheaper to purchase new, use less electricity, more sturdy floor/shelf space, better use of space (i.e. holds a lot more carboys, kegs, bottles, etc).
Pros of an upright fridge/freezer: cheaper to purchase used, much easier to get carboy's kegs in and out of, takes up less floor space.
Only you can decide what will work best for your setup. Take into account things you might want to do in the long-term as well, such as expanding your production, moving to kegging, etc. The best solution right now might not be the best solution for you next year.