Difference between freestyle and mountain snowboards?

Freestyle boards are generally softer, shorter, and wider than a freeriding or all mountain board, to make rail riding easier. Freeride boards are usually long and stiff so that they are stable at higher speeds. Freestyle boards also tend to have twin shapes, so you can ride switch the same as you would ride regularly. There really isn't that much weight difference between freeride and freestyle, it mainly depends on how expensive, hi-tech, top of the line, etc. you board it.

freestyle boards are shorter and more flexible generally for easier jibbing, jumps, and pipe experiences. Mountain boards tend to be longer and more durable to handle powder, bumps, trees, rocks, etc. It all depends on what you are looking for. Also there are different cambers and rockers to check out that can help too.