Polygel seems to be used as a generic term for a type of material - like so many complains Shellac is! Polygel is a brand name. A better way to describe this type of material is AcrylGel or Acrylic-Gel, which some people were mixing themselves long before this type of product was available ready mixed.
Many companies now offer AcrylGel and as more gel/acrylic factories offer this, more brands will buy and private label. Expect prices to drop - but make sure you know if they are selling in 30gram or 60gram sizes! Some 30gram products cost as much as 60gram, depending on brand. Like gels or acrylic, some will be better that others - so you will need to test for yourself.
For newbies, I would probably recommend starting with AcrylGel. It is quicker to master than gels and you don't have the confusion of learning to mix polymer and monomer in the correct ratio with L&P. Plus being harder than gel it suits a wider range of customers - especially those who are hard on their nails.
Of course, it is good to be able to offer gels, acrylics, acrylgel or gel polish, and recommend the option that suits the clients lifestyle. But to begin you need to make money and reach a point quickly where you can make sellable nails that are reliable.
Some acrylgels are also soak-off, we have a new acrlygel coming May that is. Personally, I don't see the benefit of soaking off but many salon customers believe it is better (without having supporting evidence). A soak-off acrylgel allows you to meet their wishes, while you can file it off and save time for the others