The best answer that specialists can seem to give right now is that if vertical tillage works for you, then do it. Research is limited, and funds are lacking to do adequate testing on the concept, at least at Purdue University. That's the word from Tony Vyn, who leads up Purdue's tillage efforts and conducts trials on various tillage concepts.
Much of the scientific work on the concept of vertical tillage has been done either at Purdue, or more so in Ontario, Canada, not that far from the northern U.S. border. So far as research studies go, it seems to help most in corn after corn, and when done in the spring. That runs counter to what some farmers are saying, or at least to how some farmers are using the various tools.
Part of the difficulty here is defining vertical tillage. Typically it's expected to be a form of tillage with straight blades where the soil is moved and fractured at a shallow depth up and down, not horizontally. Disking moves soil horizontally.
The other secret is running at a shallow depth, about 2 inches maximum, and running fast, up to or over 9 miles per hour, to get a chopping action. There's plenty of residue left on the surface, it may just be in smaller pieces than in a rue no-till situation after planting.
Various theories abound, depending upon who is making the tool and what farmers are expecting it to do. That's why it's difficult to get a clear picture of what vertical tillage can accomplish yet. It's also why it's difficult to find more than one farmer who agrees on how good of a job any one tool does, and when is the right time to run the tool.
One company, Salford, demonstrated their RTS tool in wheat stubble at the Norris farm near Plymouth last September. Norris is also a dealer for Salford. The Salford tool does a minimal amount of mixing. Company people say the concept is to start the breakdown process with residue by getting residue in contact with soil. Even they acknowledge that some farmers understand the concept, while others are still conditioned to seeing more bare soil and more tillage action. It's harder for the latter group to accept that the vertical tillage tool is accomplishing anything constructive, even though breakdown of residue can be measured over time.
Expect this debate to go on for some time. Meanwhile, make up your own mind. The other factor that may hold you back is the high price tag of the tools, from the mid-30 thousand to low $50,000 range for a mid-sized tool. Once you buy one, you're pretty much married to the concept and to that particular tool, at least in the short run.