I recently brewed a Belgian Dark ale and was comparing notes with another fellow brewer who brewed a Duvell clone. We compared each others beers and they were nearly identical in taste. What's interesting about that is how different our beers were as far as the grain bill was concerned. Mine had a lot of two row base malts but also a lot of specialty grains (Special B, Biscuit, Wheat, Crystal 60, etc.) but his was nothing but Marris Otter two row. The major thing that made them so similar was the yeast. Both of us used Belgian yeast (I don't know what he used, but I used Wyeast 1214). The yeast makes all the difference. Belgian yeast will add banana, cloves, and other spice flavors (or esters) to the beer. To many, this is the defining characteristic of a Belgian.
If you like sweeter beers you don't need the sugar. A pound of table sugar will dry the beer out and offset the high malt content in most Belgian recipes. Belgian yeasts won't ferment all the malt sugar in the wort (I haven't gotten below 1.010 with Belgian yeasts) so the table sugar is there just so the beer isn't overly sweet. It sounds a bit contradictory, but adding the table sugar will make the beer dryer.