We did a combination of both.
We had Pirates of the Caribbean themed shirts for our first MK day; Red and White theme for our first Epcot day (and first day overall); "silver screen" grey with black and red accents for first MGM day (I mean HS); and pink (free day for my DH!) for our first AK day. We had a few other shirt/outfit combinations, but on a 10 day trip, we did wash and rewear. I try to have us wear the same basic outfit combinations.
Of course I freely admit I go over the top with outfit planning, but our standard summer vacation is a three week/6,500 mile rambling road trip, so you get used to being organized. (We do NOT have matching outfits for three weeks, but I do try to coordinate our outfits and make sure they match the activity, first and foremost.)
As far as pictures, I think the coordination (I'm not one for total matching; I like things like - same colored shirt, different designs; or all same tone of colors with khakis; or very bold and noticeable accent color - also makes it easier to get DH to "play along" :-D ) makes for great pictures, but you will probably not need the outfit to figure out what day it is. The only time it might be a problem is if you wash and rewear on back to back days!