All the fisheye photos on here are taken with my fisheye one. I have yet to own or use a fisheye two, so I don’t really know a lot about it. On the fisheye two, however, the viewfinder does have a true fisheye perspective, unlike the fisheye one, so it can give you a better idea of what the picture you take will look like. It also has a hot shoe so you have the option of using something other than the built-in flash. When I bought mine, I opted for the fisheye one because a) it was cheaper, and b) I didn’t find the viewfinder or the hot shoe necessary, because it was just another toy camera for me to screw around with. I think it depends on what you want to use it for and what you want to get out of it.
Hope this helps! :)