To me screen resolution matters...with a higher resolution you can accommodate more into the screen real estate and don't have to switch things around. I used a super high resolution 15.4" laptop at work once and even having 2 dual 24" monitors didn't come closer to the productive experience that I had with that laptop...maybe it's just me but I would prefer super high screen resolutions.
More screens also means less switching things around - at least it did for me. With three screens, I almost never switched windows around. With two larger screens, I find myself moving, resizing, and alt+tabbing all the time (or expose'ing which is "cooler" but not much better).
Regardless I think it's a matter of taking time to get used to the pros and cons of a monitor layout, and figuring out what works best for you. Personally, after about 6 months with the 2 big monitors, I still miss my 3 smaller ones and will likely switch back soon.
