As usual Pete got everything right.
How much oil can an extractor siphon depends on the design of the dipstick tube. In a Mercedes-Benz engine an oil extractor can get more oil out than remove drain plug, someone tried remove drain plug first then using oil extractor after letting oil drips to no more than a drop a second, he got few ounces with extractor. Next time he tried extractor first then removed drain plug, no oil came out of drain plug. Mercedes dealers use fluid extractor to do oil change, not the standard Mityvac but the more powerful vacuum machine.
I used Mityvac 7201 to do oil change in my E430 for more than 10 years, it works very well for changing ATF and bleed brake in various cars too.
For some cars the fluid extractor doesn't siphon all the oil in the pan, because the dipstick tube wasn't designed for it. I tried Mityvac in my S2000, LS400 and most of the time I got less than 90-95% oil out of the pan.
For me personally I think Mityvac 7201 worth every penny I paid for it and more, I assign a value of $5 for oil change, bleed brake and ATF, after using it more than 20 times the value I got from it is more than $100, and I paid less than $70 12-13 years ago.
For bleeding brake, I tried various tools and nothing worked better than Mityvac.