we all want a vac oven!!
Tell us which one to get GW!
I guess the question is what you are going to use it for, because something suitable for home use and priced in the economy range, aren't necessarily the best thing for commercial producer.
If you have the mechanical skills, the cheapest way I've found is to grab a used Napco off E-Bay and replace the heating system and its controls. Pretty much a major rebuild.
The only other ovens that I've had much exposure to is the AI and now the Cascade TEK, with whom we now have a joint R&D program, to develop the ultimate commercial cannabis processing oven, but it won't be priced affordably for most home users.
As I am conservative without further investigation, if I had to buy a cheap mostly ready to use vacuum oven later yet today, I would pick up an AI and upgrade it with marble tiles on the wire shelves.
I agree that a big pump is a good thing, to save initial evacuation time, but a single stage pump will pull under 100 microns (factory tested at 65 microns), which is far too low to avoid boiling away targeted elements.
I fail to see any advantage to further pumping it all the way down to 25 microns, so that they can boil away faster, but am open to science based theories of why it is a good idea.
If you want something that is state of the art for volume, I would hold on buying for a bit and watch what our R&D venture with Cascade TEK produces. We will try to develop instrumentation to track what is in the exhaust, amongst other things, so that you can tell exactly when the desired ppm levels are reached. We will also work on cold trapping the monoterpenes from the exhaust, for reintroduction as desired later.
It will also use a chemically compatible vacuum pump, instead of the AC pumps that we've all sucked into service, but which aren't really made for the job. That will be more supportive of cold boiling the balance of the ethanol away after Rotovape, using cold boiling techniques to preserve the carboxylic acid.