texcycle I will be honest here and say that I have never bought or dealt directly with Sandy of KNK. However, I have seen how she "behaves" on the MTC forum. Before the Zing was released, a lot of Cougar owners were on the MTC forum, and even Sherri and Dawn were there helping where they could. When Sandy joined the forum to help with KNK machines, things changed. She would always answer questions on the Cougar machines, even though they weren't the machines she supported, and a lot of times her answers were wrong, including an answer to a question I had about my Cougar. She felt that because the machines were produced in the same factory, that there was NO difference in the machines. That couldn't be further from the truth. Even though the same factory makes both machines, they are made to the specs of the different companies, and they may be close but they aren't the same. IN MY OPINION, Sandy was giving false information, to sway people to the KNK machines and away from the Black Cat machines. I NEVER saw Dawn or Sherri try to sway people with false information, in fact, if you talked to them before purchasing a machine, and they felt that a different machine, even from a different manufacture was better for your needs, they would tell you, even if that meant losing a sale. I have never seen Sandy do that, she will always recommend the KNK machines that she represents, even if it is more machine than you need, or another machine would be better suited for you. When I saw what Sandy was doing, that tipped the scales for me, in the direction of Sherri at ThatsScrapInc.com.
You may not see the same things I saw in Sandy on the MTC forum now, because most of the people that have Cougars or Silver Bullets keep quiet about the machines, and get their help on this forum, instead of the MTC forum, so Sandy doesn't have to "compete" with another seller on that forum.
Also just looking at the specs of a machine doesn't tell the whole story. The Black Cat Cougar and Silver Bullets have very similar specs, they are both GREAT machines (I had a Cougar before I purchased the Silver Bullet), and the Silver Bullet seems to be just "that much" better. It is hard to describe the differences, but what Sherri and Dawn did to create the Silver Bullet makes it a better machine in the way it cuts, even though there is NOTHING wrong with the Cougar and it does a superb job as well. Most people who have a SB now, and upgraded from a Cougar, would tell you the same, that there is just something about the SB that makes it work just a bit better. Also the SB is quieter than the Cougar, when I used my Cougar (24") it has a fan that was always blowing to keep the motor cool, and I was always turning it off, if I wasn't going to be using again right away, because it was just annoying to have that noise in the background (It isn't an issue with smaller machines). When I got the SB, the first thing I noticed was how quiet it was, I could forget I even had the machine turned on sometimes, because it was so quiet.
As for the differences in the software, I will preface this by saying that I had SCAL when it was first released,and used it for my Cricut, and didn't care for it. I found MTC and used it almost exclusively until I upgraded to the SB and got a registration for the newest version. With the recent updates to SCAL, I am trying to use and learn it more as I have the time, so I may not be the best person to review the software. There are a lot of things that MTC does, that I'm not sure SCAL does. They will both bring an image into the software to create a cut line for it. I use either Inkscape or MTC for that as that is what I am used to, so I couldn't say if SCAL did a better job or not. They both can send your design to the cutter, I think SCAL does a better job of communicating with the SB or Cougar, especially for larger, node heavy files, as mentioned previously. Brandon, the developer of SCAL has worked closely with Dawn to make sure SCAL does a good job of working with the machines. With MTC, there is a Black Cat plugin for using with the machines, but most people use the KNK plug in, which also works, but it doesn't seem to do as good of a job as SCAL with our machines. I tend to do most of my designing in either Inkscape or MTC depending on which one I "know" better for a particular thing I want to do and if I have the time to "learn something new" with the software, or if I just need to get it done and move on. But I do almost all my cutting exclusively with SCAL. Since you can export your designs from MTC as an SVG it is easy enough to import them into SCAL to send to the machine.
Sorry for such a long post, but I hope this helps answer some of your questions.