the draining method will remove all the fluid from the vehicle and prevent the suck and flush which is time consuming. Once it drains just do the other stuff you need to do it really is very easy plus you will not introduce air into the system on refill. Have fun. The suck and flush method is effective, it is similar to not draining the torque converter when changing the tranny fluid as long as you do it a little more often it should be fine.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)