transmission - flush vs drain

I am completely confused - one local dealer does drain, another flush, one transmission place says they do flush, another transmission place says they don't believe in flush and only drain. Anyone has any ideas on the subject, especially in regards to Kia Sedona?

Thanks.

Flushing the transmission is the process of forcing in new fluid to "flush" or force out the old fluid. It removes more contaminants such as metal, dirt, etc. and assures that the new fluid that is put in is as clean as possible. Draining is simply removing the plug and letting the old stuff run out and then refilling with new fluid. The problem with this is that not as many contaminants will be removed. Whatever happens to run out with the old fluid is all that is removed. Particles are left behind inside the transmission if they don't run out and then these particles contaminate the "new" fluid that is poured back it. This fluid is cleaner than what was removed, but not as clean as fluid put into a "flushed" transmission. Hopefully this clears things up for you. Simply put, flushing is better.