1. No gyms, all confirmed main series games have gyms. Well, there is one gym, but that doesn't count.
2. No wild Pokemon (except for XD's inconvenient system)
3. No option to play as a female character.
4. Not on a handheld system
And more.
But don't get me wrong, they have obvious similarities, and are more like the main series games than pretty much any other spin off.
