They have different strengths.
Tumbler is very effective at removing sand and can be used to fix nap distortion after cleaning. Relatively cheap. Few moving parts; bearings would be the only routine replacement part.
Automatic can handle rugs that can't be crumpled due to stiff or weak backings. For a production cleaning biz, they're required, as tumbling a large quantity of rugs would take too much time. Bigger footprint, much more mechanically complex, but not much maintenance required.
Best for you depends on what type of rugs you're cleaning most and how many. At some point you'll want both.
I have used both over the years in my small business. Naturally, I have a preference.
First: Let me make a full disclosure. My company designs, builds and sells dusters under the brand names Centrum Force and MOR Time Saving Equipment. The MOR brand has been making dusters for the industry since the 1950's. Centrum Force brand was introduced in 2007. Safe to say we have well over a couple of hundred dusters out there working worldwide.
Having said that, for effective dry soil removal, the Tumble Duster is the best. However, not all rugs can be safely put inside of it for processing by tumbling. One needs to know rug construction to avoid mishaps to rugs that should not be submitted to the tumble.
The flat bed Automatic Rug Duster, such as we make, and as Bryan indicated, has assembly line production value. You give up some quality in dry soil removal to gain speed for rug processing for the wash phase. Albeit, some rugs should not be submitted to this form of dusting due to rug construction considerations too.
Addressing production comparisons:
I know of at least one in-plant operator that opted to install two 10' Tumble Dusters. That keeps up with his production and quality with about the same investment that would have been made to acquire one Automated Rug Duster.
Consider, two Tumble Dusters can be loaded with well over 40 rugs at once. Set the timer for 30 minutes and walk away and do something else with your labor. One flat bed Automated Rug Duster requires a person or two to feed each rug individually into the machine. Those operators are dedicated to work with that machine to process those same +40 rugs. Depending on the rug sizes, the jury will likely be challenged with how much more labor was dedicated to one over the other. But you will not get the same results. (Note: I randomly just picked the number 40 rugs. Truth be told, it could be higher depending on the rug sizes)
Feel free to call me and talk this out.
'Different strokes for different folks.'
As far as long term maintenance, at least with what Centrum Force makes, it's minimal. Mainly, occasional lube the bearings for the shafts that spin. The belts on the Automated Rug Duster or the metal straps on the MOR Duster will need to be replaced only after many years of service. We have seen that in some cases, that time has be a decade or longer.
Note: You can still buy a used MOR Duster around the country for under $10K. Why? Because companies have replaced them with a Tumble Duster. Let me know if you have interest in a used one. I know where at least 3 are located.
No question Tumbler. As the Oz points out you can't run everything in a tumbler but the qualitative difference is amazing. If you are big enough both make sense we've talked about having a strap duster and everything that comes in goes through the strap duster and on to the wash carts or into the Tumbler duster.