I have a Tecomec and a Knock it Off grinders. The Tecomec is the better machine. One thing you can't tell just by looking at them is the new Tecomec/Oregon units have a self centering chain vice, making your life that much easier. The biggest gripe I have about my knock it off grinder is every adjustment screw is either too tight or way too loose threaded. It will sharpen a chain, no doubt, just not as user friendly. If I had to start over again I would purchase another Tecomec/Oregon, as there is parts support, clear instructions manual, ease of use, better wheels and so on.
No matter which way you go don't worry how your first chains come out, they will get better as you learn along the way.
EDIT: Almost forgot, another thing I really like about my Tecomec is the forward and reverse rotation. My clone is one direction. Not sure what new ones feature now days as the Tecomec is getting a bit old now.