Warrior or guardian - pve/wvw
I don’t PVE so I can’t comment on this.
For WvW, when it comes to roaming it’s a matter of personal preference. Guardian has a smaller health pool but at the same time blinds and blocks which a warrior doesn’t have. Meditation builds are the most common for guardian roamers and has a higher learning curve over typical destroyer warrior builds.
In larger scale combat (15+) guardians are requested more than warriors because of skills which provide might, stability, and protection. Even though both are equally important, it’s harder to fight if a party is short a guardian than being short a warrior. Even in this type of combat style guardians also have a higher learning curve over warrior because of the increased number of cool downs you have to manage.
Guardians:
Provide stability, protection, might, and regen
Small amount of AOE healing
Short cooldown on blast finisher for waters
CC’s enemy
Warriors:
Provides might and fury
Clears soft CC’s
CC’s enemy
Two different blast finishers for waters
Can revive downed allies
Two guardians are needed in melee parties for amble stabo/prot uptime and max might stacks on empower
Two warriors are needed per party for amble fury uptime. Most competitive guilds include the fury gained from For Great Justice in their builds when optimizing their stats.