No, that statement was made with the current Paladin in mind (though before the latest major patch mind you). It has a couple of meanings:
1) If all you want to do is tank, Warrior is the better bet as they have 2 roles: DPS and tank. They are the best tanks in the game all things considered and are by some still thought of as the only 'viable' tank in the game. Someone thinks Warrior, they automatically think tank. Someone thinks Paladin they won't always, if ever, think tank and may very well question or laugh at you for being such.
Paladins though have all 3 roles available to them, so if you want to be more flexible, Paladin is the better choice because there is more you can do (respeccing for Holy to heal or DPS, soloing group quests with ease, farming lower level instances with ease, etc..)
2) Warriors have since day one been tailor made to tank. That is their purpose, and while a Fury and/or Arms Warrior can surely put out respectable DPS, their primary role/purpose is to be the squishy guy's meat-shield. They take less damage than other tanks, have more abilities for tanking that do a wider variety of things, and don't have the "new kid" stigma that Paladins, and even to some extent Druids, have.
Now that the statement in question has been addressed, a response tailor made to your situation:
Paladins are hands down the best 5-man tanks. Our tanking abilities revolve around damage done to multiple targets making the need for CC in most cases null-and-void. Our Taunt is even tailored around AOE by having such a long range and affecting up to 3 targets at a time, while a Warrior needs to be in melee range to Taunt and it only affects one target at a time, barring their Shout which has a much longer CD. Paladins also bring a set of buffs with them that another group member may not have making them able to fill a bit of a support role while tanking. To top if off, if things go bad a Paladin can at times last through any remaining mobs and rez the group on their own where a Warrior can not, or DI the healer to prevent a long run back to the instance. Also a quick heal-to-full can sometimes make the difference between victory and death.
Where Paladins lack a bit to Warriors is in staving off damage. Warriors can use Demo Shout, Thunder Clap, and they have a higher damage reduction in their Defensive Stance then we do with our RF active. They can also go immune to fear making some fights much much simpler (read as Nightbane, that first boss in Shadow Labyrinth, etc..), have an easier time with caster mobs, Spell Reflect, Shield Wall, and some other cool moves along with a faster/higher single target threat gain.
As one who would be doing mostly 5-mans, and with PuGs, I would advise a Paladin over Warrior.