To each his own. If you're happy with the under-car method, go for it. On the other hand, if you search on "topsider", you'll uncover more info than you could possibly be interested in. One piece is very relevant, though, and that is an experiment where the topside and under car method went head-to-head and the topside actually drained out MORE oil than the gravity method.
I also like the convenience of sucking the oil right into the storage receptacle, instead of draining it into a drain pan, then pouring the oil into some sort of container to take to the recycler, then cleaning the drain pan, etc.
For what it's worth, most MB dealerships are equipped with oil tube suction machines for extracting oil, and MB has designed their engines since the 1970s specifically with this method in mind.