As to this question, there would be many factors to which drumstick you should buy.
For example
1) Type of music that u play, 7As are more for lighter stuff, like blues and jazz, whereas the bigger sizes like 5B are for rock
2) Style of playing, whether the songs u play require solid hits or speed, if u want more solid hits, then get the bigger sizes and heavier sticks because they can project louder than thinner sticks/lighter. If the type u play requires speed, get the lighter sticks, but make sure u buy the right size, as if u buy too thin a stick, it may slip out of your hand when u are playing fast.
I currently use Vater, i have tried Vic Firth, Zildjian, Los Cabos, Lazer, and other brands.
Vater sticks are heavier than usual sticks, compared to Vic Firth, giving more control. Whereas the lightness of vic firth sticks make it easier for speed playing. Vater sticks are usually smooth, so u can get both speed and control(weight). Vic Firth sticks are smooth too.
And the thing about Vater, is that, they're damn durable, i've never broken a vater stick before, but i've broken vic firth, zildjian sticks. I still have a real worn out Vater 7A set of sticks that i used for 5 years!
Hope this helps u with ur decision