It is not night and day but you can tell the improvement after a few of your favorite tracks, the treble sounds "sweeter" and it can render complex orchestral pieces better, on the looks department I don't care much for the white cones. The bigger motors supposedly allow the Be to handle better heat and in turn dynamic compression but I have not pushed them that hard.
IMO if you have the cash, go for the 228Be but the 208 will be enough for most and you can invest in subs or amps. It is the same situation as other high end audio devices, 50% of the price gets you 90% of the performance. As a matter of fact, I have also heard 208s alongside 126Bes and I think the 208s are a better bargain unless you put them in a 4 square meter room.