I'll recommend mostly GNU/Linux; its the best
tool for most jobs an OS is useful for.
Beyond that I'd consider
- support; does it have support sites you'd like to use when/if you get yourself into trouble
- if you have friends/family/workmates who use a GNU/Linux distribution, using whatever they use (or something close to it) maybe beneficial (variation of my first support point)
- duration of support; ie. does it have long-term support releases? or only shorter life releases, as there is great variation in that, and for some end use cases of installing an OS you want the release to be installed & survive for years without needing to perform release-upgrades, and don't care about always having the latest software, just that it's stable and keeps functioning reliably.
In the end, the distribution used
mostly varies
when the code/programs/apps are grabbed from upstream, in what format they're
packaged which alters the commands
slightly, with some variation available with a distribution based on support length, security checks etc..
Each situation (
ie. end-use you'll use the install for) will decide what is best, myself I'm partial to Debian & Ubuntu most, but I could live on almost any GNU/Linux system, or even a BSD system too (
though I stopped using BSD as I just found GNU/Linux so much easier).
We all have
favorite or different ideas on what
flavor ice-cream is best, every GNU/Linux distribution likewise has different
pros and
cons, so use the best for that particular end-use case, and use another in another role; ie. use the best
tool for the job, and GNU/Linux gives you a lot of great tools to choose from.