This my opinion, anyone still continuing the path of the warrior (now that I think about it, any tank, actually), should correct me...
At the moment, Vanguard and Plate are both heavy armor and have roughly, if not exactly, the same stats. They look different. Plate actually looks like rusted chainmail. :/ Or it did before the Big Patch Part Deux. I don't know what they look like now if it changed.
Berserker is a more offensive tank. Does more damage than a Guardian and has access to more offensive skills (like bloodlust). Guardians are the defensive bent. They have many "guard" abilities and tank mostly by damage mitigation, if memory serves.
Paladins and Shadowknight are tanks, just like Zerkers and Guards, Monks and Bruisers. It has been made apparent, to me at least, that any class/subclass from the Fighter Archetype is a tank.
I can't say what is most desired end game, but I personally don't think it really matters _that_ much.
Choosing a subclass is more about personal style, I believe. When I started my Guardian, I didn't care that I wouldn't bust out the damage numbers. I wanted to be defensive... and I admit, the Guardian subclass was one that I wanted to roleplay with.
VS threads do you no justice when deciding on a tank. Rather, find out the styles that are required for each type of subclass and determine if that style is how you want to play.
FYI, I solo'd my Guardian for most of his career, up until he disappeared in the Bramble Wood. I've also played MT and backup tank in some situations.
Edited, Tue Feb 1 20:35:58 2005 by ArcosKojin