Also, the map style has changed. TA is the last module to support the old style (it contains both styles). If you want to go beyond TA, I'd get the new stuff.True, I almost forgot that the old edition has different art and thinner boards. I've only seen one board with the old style (the one from TA), but I don't think that's worth buying a whole new copy of SE for.
The old maps can be sued with the new ones, they'll just have a slightly different thickness and different artwork.