OSX is very popular in astronomy because of the combination of commercial and open-source tools available for it: i.e. you can run Word, Excel, Matlab, Mathematica, IDL, iraf, ds9, et cetera.
Personally, I prefer Windows and I have found a combination of Windows and Ubuntu can combine to run pretty much anything. Technically, you can get most UNIX software that astronomers use working under Cygwin, but it can be a real hassle (getting working under Ubuntu and OSX can also be problematic).
However, I have to say that hands-down, the best two planetarium programs out there are:
1) Microsoft Worldwide Telescope. This is free software that gives you access to huge astronomical databases. This program is used by the most advanced planetariums in the world. The downsides are that it requires a constant internet connection, Windows 7 or better (there is a java version that lacks most of the best features), a good graphical coprocessor or two (this program is used to drive some of the highest-resolution screens in the world so it can be GPU intensive depending on your setup and may be unsuitable for laptops without a good discrete GPU), and the level of customization of some programs.
2) Starry Night: this is a great program, but it is also expensive and OSX and Windows only.
Open source planetarium programs range from mediocre to quite excellent. The ones you mention are probably some of the best, along with KDEStars.
It's hard to get too far in astronomy or astrophysics without some kind of UNIX access, whether it be cygwin, OS X (seems to be the most popular), Linux dual-boot/VM/discrete workstation, or UNIX server access (Solaris/ HP-UX/BSD seems mostly to have died in physics/astronomy except for big servers or legacy workstations).