Paul and Haasman
Paul - Bertie has been added by special request - see slide 8. Unforgivable oversight on my part.
Haasman - the factory suction method attaches the suction device to the TOP of the dispstick tube (based on the illustration in the W126 Maintenance Manual) so it can only suck out to the base of the dipstick tube in the oil pan. After that it's sucking air. The Topsider method sucks out to somewhere below the top and bottom of the slash cut (if you use one) - the bottom is, of course, actually in contact with the base of the oil pan. (I realize you know this as a Topsider user). The slash is some 3-4mm in vertical height.
I don't know the clearance between the bottom of the dipstick tube and the base of the oil pan, but the Topsider will be as good or better, by definition. I suppose you could measure this by comparing the length of the disptick with the length of Topsider tube that is inserted to the base of the oil pan.
For everyone who uses a square cut Topsider tube there will be an 'expert' who will tell you that you should use a slash cut, blah, blah, blah.
I actually am coming around to thinking that a square cut makes better sense as if it contacts the base of the pan it cannot be perpendicular to the pan (and allegedly stuck as a result) for the oil dipstick tube is not perpendicular to the pan, and it's the oil dipstick tube that determines the angle of the Topsider tube.
Further, even were the Tospder tube to get stuck because of a perfect suction to the bottom of the pan you would immediately know this as no oil would come out.
Now I'm going blah, blah, blah.....