Okay so i'm a bass player not a drummer but i do have a set and i mess around on it sometimes.  normally when i play i keep the beat with my left hand even though i'm right handed.  my friend who's a drummer said that i should be using my right hand, but he can't really tell me why.  is it just preference or is there some biological balance-thingy-reasoning for that?

Actually, leading with your left hand gives you a better range of motion because you can freely move around the kit. You don't have to bring your left arm over the right to do any fills or anything.

It's a great time to be a drummer. Don't feel you have to follow convention - do what is comfortable and have fun.

Check out Josh Eppard. He's the former drummer for Coheed and Cambria and plays a righty set with a left hand lead. It's genius in my opinion and I wish I could do it but sadly I cannot. Like the others have said it gives you a free range of motion with little crossover interference. Plus it just looks cool.

As a drum set drummer, you have to keep time with your entire body.  All four limbs need to work in synch with each other.

Well yea, but it's possible to be in a mind set where the other limbs are simply slaves of one. If you can think interdependently then you should say, be able to remove your right hand, stop time keeping with it, but continue to play in time, or say, switch leading hands.

Exactly -- if your time is dependent upon you keeping a steady 8th/16th/trip pattern going, you're going to get easily dislodged or off time. Feel the pulse with your entire body -- it'll help with keeping you on time out of fills as well. Plus if you aren't leaning on your right hand to keep ticking away steadily, you are more free to drop a note here and there to great effect.

(That's more just to keep you from making the mistake I did of kind of slaving my body to my right hand -- really messed me up for a long time.)

Traditionally, though, drummers keep a steady pattern going with their dominant hand for the ease of it. Open-handed stuff, etc. is just icing on the cake.

BOTH! You can have a rock-solid right hand and play the cleanest 8th notes all day long, but if your left-hand can't play 2+4 in the right place, it don't mean squat.

Trying playing ostinatos with both hands and accompanying with both hands.

Sometimes I'll keep time with my left foot on the high hat. When that isn't useful depending upon the song. I'll just pull my foot off and not use it. Our band singer has a problem when I use the floor to keep time. He hears that time and complains that it bothers him. So I've gotten used to just keeping time in my head. Brain power wins again.   

I would just take my foot off the pedal, and thump it on the floor or whatever was there. I didn't listen to it, I just felt it thump. Strangely, the singer would hear it. I think he just wanted something to gripe about, he's just that kind of guy.   

alright thanks for all input