Hi Tony,
I would recommend the 16x20. It gives you extra room that helps with lining up the clothing before pressing. It also allows you to press larger transfers when needed as designs change or design trends change. You can also press more than one item at a time occasionally, like mouse pads as an example. That being said, there is nothing wrong with a 15x15. It is a very useful size and can accomplish almost anything you will need to do. In my opinion, never go any smaller than a 15x15. Also, the vast majority of heat presses in use, from what I've read, are the manual clamshell type press. They take up less space than swing away types, require no compressor, and in general are a proven design that will last almost forever. There are advantages to having a clamshell type press just like there are advantages for having a swing-away, or a fully automatic air assisted press. If you are starting out, or are an established company, you can't go wrong with a good quality clamshell. I prefer Hix, but there are a few other quality manufacturers as well. I think the two biggest mistakes would be buying a press that is too small, and buying a press from a company that hasn't been around long enough to prove their dependability. Also, once you have chosen your desired press, don't just shop by price alone. Buy from a dependable distributor that is willing to provide guidance and customer support and happens to have a good price.
