Roll arms warrior because they are so cool and it is very intimidating when you're charging to a group of enemy, a huge mass of steel and muscles moving towards you at a velocity not even the mightiest of feline swiftness speed pot darkflight druids can ever accelerate to! Hacking and slashing with a weapon of your choice, dealing huge amounts of damage, getting your powers from a resource called RAGE! They survive through the most epic of battles, tearing apart, annihilating every opponent in sight. You can STUN opponents, reduce their healing, execute them with mighty crits of over TWO THOUSAND and much more!
If that's not enough and you want to be the heroic carrier of the Warsong Gulch flag, you can spec into protection, being a bulwark in plate armor, carrying a shield in other hand and a weapon of choice in other. Backed up with healers you are close to immortal, having easily the biggest damage mitigation a level 19 can achieve.
Holy shit, how fucking awesome is that, is there nothing these battlemasters can do? The answer is no.
TLDR; Try to find out what each class is capable of doing (CCing, damage, healing, FCing, midcontrol, etc), think of what you are interested in playing at the 19s and overall, choose a class and go for it. Gear to as close as BiS as possible, go try it out on battlegrounds and see if you like it. If it doesn't feel the right class for you, there's always 9 more classes that you can try

Feel free to ask me any questions and information about the 19s on PM mate, I will do my best answering anything that you need to know!
ps. sorry just wanted to write something, but the TLDR is all tru
Disclaimer: Warriors might not actually be as OP in game as I described them to be.