It really depends what kind of a playstyle you are looking for.
Beserker stats (Power, precision, Ferocity) is usually a safe way to go provided you have other bits of equipment to provide a bit of vitality and toughness.
Personally, I run Soldier stats (power, toughness, vitality) in my chest, gloves and leggings and everything else is zerker. Its all down to personal preference.
As for upgrade components, again that depends on your playstyle. If you run shouts, things like Runes of the soldier are an amazing thing to have, but it would restrict your playstyle to a shout build. DPS wise, runes of the eagle etc will turn your guardian into a crit machine.
(edited by Weo weo.6378)
I think guardians are usually agreed to be the most well rounded class out there. Although they have a low health pool, they have many reactionary skills, heals and blocks which make them one of the harder classes to take down. Lots of condition removal, boons for the team and virtues which both have a passive and active benefit. They also hit quite hard as well if specced to be so. Basically, they are one of the most favored classes in PVE and in WvW teams simply by the fact they benefit everyone around them.
Only thing they truly lack is mobility, although depending on the weapons used, they have a fair number of gap closers in combat.