if your budget allows it, i would go for the 17". the 15 will do just fine, but if given the option, definitely the 17" with the anti-glare screen. however, if you don't want to lug around a big laptop like that, a 15" will do you just fine, as well. just stay far away from the 13" if you plan on working in photoshop.
i worked on photoshop and lightroom on a 2006 white macbook for 6 years and i felt very, very limited with screen real estate (obviously). granted, i just bought a brand new 13" air, i only bought the MBA because i needed a new computer and will definitely get the 17" pro when the new models come out. the mba was just something to hold me down until then and to help with portability when i do get the 17".
if portability is a big factor for you, stay with a higher-spec 15" pro