Yes but huttball is the only one you can fight against your faction, and groups are limited to 4 man queue's.
In a standard WZ match you don't have the opportunity to see, guide, train, whatever with other people and not have the looming threat of the opposing team breathing down your neck.
A prime example would be you have people who are new to or scared of PVP and new their classes and you want to teach in practical ways the importance of certain skills, gear, and most importantly tactics which you simply cannot do in a dual situation.
Or people that just don't understand the importance of certain things.
How often have you beat your head on on your desk when your guarded healer ran off to another area to get in the fight only to be slaughtered. or visa versa. How often does your own team, or the other team become a laughing stock as every player runs around like the 3 stooges with no plan of attack what so ever.
It would be extremely beneficial to be able to help, and to be helped in learning better ways of running WZ's.
Yes there is open world pvp in whatever forms you choose but they are fundamentally different animals.