I started with an HQ16, upgraded to an APQS Millennium. There's no comparison really. If possible, it's always best to try out the machines. If not, do your research and go with that.
You can master any machine. I think my Millennium is fabulous, but I chose it because they have an 8 year warranty (longest in the business) and outstanding, friendly support.
They also have a very popular online forum, lots of help and inspiration available there.