I’ll chime-in. The Altmill actually looks like a good machine. I may be biased towards C3D, but it can’t be denied that on cost and features, I consider the Altmill the best competitor. It looks to be a great package and you probably get a good machine either way. Looks like a mostly well thought-out video. I would like to see more like precision and bed rigidity investigated. I’ll try to point out some areas for more info more so than disparage any brand. In all good competition is good for us consumers in this case.
Differing Features: To further the complexity of the equation, the Altmill doesn’t have a bed, BitSetter style solution, workholding, etc, so it is less ready to run. You have to figure that out and pay for it separately. Rigidity is nothing without workholding…seriously the hybrid bed is peak workholding for functionality and versatility. So that changes the cost equation, useability, and how much time it takes to get it running at first. I will also note that I HATE those tall work clamps he’s using on the Altmill for CNC work. Those things are great for an assembly table, but are a danger to endmills. 
Rigidity: The Altmill does look to have a taller X gantry extrusion. That does help in twisting. But I would also like to see how they do in lateral and longitudinal deflection on the motion system. Twisting is likely the more limiting factor in the motion system though. The base extrusions are also taller and that helps. But I would like to see the deflection of the bed. Both areas of deflection are very important. C3D has both longitudinal and lateral support on the bed. He does not test bed deflection in the video.
Motors: One factor this video doesn’t take into account is the ballscrew pitch. The steppers may have more holding power/torque, but the ballscrew pitch comes into play when you’re factoring in actual torque. Looking at the Altmill ballscrew (I’m just going by what I can see in the video, as they do not have specs) ballscrews, they look to be a coarser pitch. So that means that it sacrifices torque at the ballnut and precision in exchange for speed. I can’t say that’s huge, but it is a factor in how much torque there is at the actual cut and not just at the motors. The closed loop is nice, but from what I have seen, it does less than most people think it does. I could be wrong there.
V-Carve Race: It’s been hit on, but unless the software is apples to apples, it’s a moot comparison. Is the retract height and speed the same for instance? The difference is that C3D has a free design/programming solution, Altmill doesn’t. In a real world v-carve you usually have a tool change. The Altmill not having that and needing a Z reset would add real world time that the BitSetter greatly simplifies.
Cost: He didn’t add in the cost of the bed, extrusions, wasteboard slats, and clamps to the Altmill, all of which comes with the S5Pro. Again, a CNC and it’s rigidity are useless unless you can actually hold the material in place. A Baltic birch sheet for the bed runs ~$140 where I live. A sheet of MDF is ~$50 at Lowe’s. Powertech extrusions would be ~$85 for 8 of them that are 48" long. The clamps he’s using (again, I hate those for CNC work) are ~$30 for a 4-pack. So that is an additional ~$305 to add to the Altmill physical cost in his own comparison. If you also factor in a license of Vectric VCarve Pro (so you can use the whole bed of the machine as the base version only lets you cut 24"x24"), you’re adding another $700 to be able to use the Altmill at all unless you find a free program, and those have less features than Carbide Create. For the table cost on my S5Pro 4x4, I personally went overboard with a Rockler Rock-Steady bench frame and two butcher block style pieces for the top. I think I’m in $500-ish on that. And a Windows tablet is $300-ish. So they are pretty much a wash-ish depending on your load out. A S5Pro table could be built for a whole lot less than I spent. So all factors considered, the price I would say is a wash, or actually in favor of the S5Pro. But it’s not far off either way.
Beer: I guess I’m pickier there. I will pass on bad free beer. 
Edit: Grammar because it’s been 35 years since elementary school.
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Adam Savage says the difference between play and science is writing stuff down. I will add that it is also measurement.