The G2 frame does not accept 12 or 20 gauge barrels. It is a smaller frame and while it looks like the Encore, the barrels are incompatible. Generally, .410 is the only shotgun barrel available for the G2 although there may be a custom 28 gauge out there somewhere. The Encore is stronger and heavier than the Contender and can take much more potent calibers such as .300 Win. Mag., .454 Casull and others that would take a G2 apart. The Contender can do rimfire right out of the box while the Encore can not without a special adapter. Look at the Fox Ridge web site (T/C Custom shop) or Bullberry's and check out what calibers are offered in each. Figure out what calibers you want to try and what frame supports that. That will pretty much tell you what frame to get first.