[Andrés]

Rock and Ice are definitely equal in appearance for...

Actually in the stock game ice planets are only slightly more common than gas giants and of the same size that rock ones, so being native of ice planets is a serious handicap.

Also rock-methane has a slight advantage over and ice-methane a slight disadvantage over other atmospheres.

I had made calculations of chances of appereance and planet sizes long ago, search for a thread called "are gas giants really an advantage"

I don't know if mods such as the FQM attempt improve that balance, by forcing some planets to be ice in the system files, or in case of the deluxe Version by adding more ice planets sector types.