Does what it's supposed to do and has the best reviews compared to others on the market.
First time using it, pulled about 4L of old engine oil using the bigger dipstick tube out in less than 10 mins.
I've researched these other models as well, but the Mityvac 7201 (specifically the 7201 and not the 7400) has more general positive feedback overall: Topsider Mityvac 7400
For the Topsider, you read about a lot of issues with it losing vacuum. I think that's because there's no separate pour-out hole, like the 7201 has. You end up having to keep removing the pump mechanism, and that wear and tear causes those sealing issues.
For the Mityvac 7400, you read a lot about seal & pump issues - especially when fluid is left in the reservoir. The reason is because the pump is contained within the reservoir, not outside like it is in the 7201, and old fluids left in there cause damage to the pump mechanism over time.
Some tips on using the Mityvac 7201:
1. Cut a small 45deg cutout on the end of the hose that will go into the oil pan. This is to prevent the hose's end from forming a complete seal on the bottom of the oil pan, which will prevent any liquid from flowing through the hose. Search the web for some forum posts talking about this.
2. Practice first on a bucket of water. Press the bigger hose into the hole on top the unit, next to the cork. Connect whichever smaller hose works for your car's dipstick hole to the bigger hose. Put the smaller hose into the bucket of water. Pump the vacuum 6x. You'll see and hear the water start to go into the reservoir. You can pump a couple times here and there as it's picking up the water, to accelerate the process. Near the end, you'll hear a gurgling sound as the bucket is almost empty. Keep pumping while you guide the hose around to suction up all the remaining water.
The idea is that you'll use this knowledge to help you, when you're doing it 'blind' with the engine oil extraction - because you won't be able to see what's happening within the oil pan.
3. Use as 'One way' for Extraction only. Meaning, always keep it in the Extract mode (button pushed down) and try not to use the Dispense mode. Just empty reservoir using the corked pour-out on the top.
My reasoning is that this will result in less wear-and-tear and prevent gunking up the mechanisms and tubes with old dirty oil. Especially after reading comments about the Extract/Dispense switch o-rings failing over time.
4. Clean after use by suctioning brake cleaner or some other type of engine oil cleaner, swishing around and pouring out through top.