lets clear up some terms here. if you are dropping your tranny pan replacing the filter that can be considered a tranny service or drain and refill.
if you use a flush machine it is considered a "flush" you are not likely going to have one of these machines at your house.
as the are quite pricy.
that said I would HIGHLY reccomend the tranny flush and here is the reason with a example. first the example.
I decide to do a tranny service or drain and refill on my car so I drive to autozone and ask "how much fluid and what kind" they say oh 5 qt dextron/mercon so I buy 5 qt and drive to the ford dealer because autozone dosent have the gasket and filter. I then get home and drive my car onto ramps, get out the drain pan and start unbolting the pan, btw there is a order to do this unless you want to cover everything in tranny fluid. I start on the pointed side and work my way to the driver side of the car* but not removing 2 of the bolts on the long flat side (driverside) remove all bolts except those 2 just start loostening the 2 and it will slowly lower your pan thus having a controlled drain. I replace the filter bolt up the pan and fill it with 5 qt of fluid. start her up and check the fluid. its low but driveable, it ended up taking 7-8 qt.
that said (now that I've waisted 3.25 minutes of your time)
when you drain and refill you only take about half of the fluid out, and your not really cleaning anything. However when you flush your tranny a detergent is put in to clean all the crap out then they hook up the machine inline with a cooler or other tranny line. the machine throws away your old fluid and puts new clean fluid inplace of it. took between 17-20 qt (average would be about 15 on our cars) to CLEAN out my old tranny, but then again it wa cooked, two months later to die. (long story)
morral if you have a friend in the business get it flushed. but don't get me wrong I would still recoment a drain and refill over nothing any day... as long as you replace the filter