Madeira/Porto

[Jason]

From a taste perspective, Madiera is always more acidic to me. I find this to be a good thing as it balances the natural fruit left by arresting the fermentation. Madiera is generally varietally labeled. Strangley enough the older it gets the drier it gets.
A 10 year Malmsey by Blandy's is a favorite.
There are also two major flavor types of Porto, ruby and tawny. Ruby is much more like red wine and is very deep and fruity, good with cheese. Tawnies are much more amber in color and have more of a caramel character. The classic with these is flan or creme brulee.