It runs fine on both as people here will tell you. The only thing is that for most of us unix is easier to set up and use (easier to set access rights for example).
Actinic will most definately run quite happily on both linux and windows servers, but it is all down to getting the right host and right settings created on the server to start with, so although the largest proportion uses linux, windows can do it also, but due to the increased issues that Actinic users experience through 'shall we say - not so well put together windows servers - from an Actinic usage point of view' is why more gripes come up about windows servers than linux..
Not a complete answer I know, and would suggest that if your host can provide linux, then go for that, but again, windows servers can happily host actinic in the right conditions of setup.
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