I found the following comment influential as I was choosing my first chamber vacuum sealer. Slight modifications have been made from the source to improve on clarity.
The three most important components that differentiate a quality vacuum chamber sealer are the pump, the pump, and the pump.
A dry pump will not pull nearly as high a vacuum as an oil pump.
An oil pump will last far longer than a dry pump.
All pumps slowly lose their maximum vacuum with use, but dry pumps will do so much faster than oil based pumps.
Busch pumps are at the top of the food chain, followed by DVP, followed by the VP mystery chinese oil pump, in terms of quality and maximum vacuum.
Serviceability is another major issue. Busch pump parts are widely available, and the pumps can be restored to “new” condition for about $375. The lower end Busch pumps (16 and 21 m3/minute) found in the smaller chamber machines are rated for 730,000(!) cycles prior to a rebuild. Good luck getting that VP pump fixed in a few years.
While price is not always an indicator of quality, it is worth noting that the smallest Busch pump (just the pump) costs more than a VP210.
Personally, I’d rather spend $2,000 on a Busch pump based machine that will, in a home environment, probably last forever, than $1,250 on one with a questionable, perhaps impossible to repair pump.
As to the other features like vacuum by percentage, vacuum by H2O sensor, soft air, gas flush, etc…they’re nice to have, but it’s the pump that matters most.
Source: GlowingGhoul on eGullet.org forums, http://forums.egullet.org/topic/137429-chamber-vacuum-sealers-2011–2014/?p=1853446
The only problem with following this advice is that you won’t find Busch pumps in entry-level chamber vacuum sealers.
They are featured in Henkelman’s vacuum sealers (http://www.henkelman.com), but these retail for several times the price of entry-level units. Such an investment puts the best pumps out of range for most home sous vide enthusiasts.
GlowingGhoul might say that I’m taking a gamble on my decision to order the VacMaster VP215. The good news about the VP215 is that there are replacement parts available for it. I can purchase a replacement pump to keep on hand for when the original pump does fail.
The comment is still useful.