What's the difference between administering Mac OS vs Windows machines in terms of :
- difficulties encountered
Depends on what you mean by difficulties. The tools for administering the machines on a LAN are not as mature and well developed as the ones for Windows, so things that a Windows admin would normally do easily enough with Group Policies may be frustrating on a Mac LAN at times. Apple seem to be completely clueless about Systems Administration needs and requirements at times, so you will find some areas are very easily managed and other things that require a lot of time and trouble to get right. And it may well be the obscure things that are easy and the basic things that are difficult.
However, OSX being based on UNIX means that you have a wealth of tools and stuff available from that world to help you out.
One area that may complicate mac systems administration in the future is their dropping of the xserve and only having limited options available to run OSX server on now (The Mac Mini and Mac Pro are fine choices for a small business or branch office but might not work too well in a datacentre environment). Depending on the size of your mac environment (and therefore the amount of server-side stuff you need to administer them well) you may find those inadequate or difficult to work with.
Being based on Unix, the mac generally uses the Unix security model (e.g. for permissions, user access, etc). Being a Mac, it has a few twists of its own to this model and a decent gui interface to make using this fairly simple.
Modern Mac OSes also support ACLs for things like file permissions, so in theory you get the best of both worlds. In practice... it works well enough but you can still find a few frustrating areas here and there.
- the number of calls to the helpdesk (is it lower?)
We get less calls for our macs than we do our windows machines, yes. I mean we get less calls for Macs than Windows machines because we have fewer macs, but we also get less calls proportionally, if you see what I mean. However, we still do get a few calls, especially from people who have never used a Mac before and struggle because its different to what they are used to.
At the end of the day, the biggest cause of calls isn't usually the OS itself but rather the applications, so I suggest that the applications are where you should be looking.
Our Macs generally run MS Office (and we do get some calls on that, usually where its not 100% compatible with our Windows version), Adobe Creative Suite (actually causes us less problems on Mac OSX) and Final Cut Pro (A very specialist bit of kit, we don't get many calls about this at all but only because specialist training and hand holding is given to people who use it here).
If you run a mixed environment then you can expect a few extra calls from all the platforms you support along the lines of "I know how to do x on OSbar, how can I make OSfoo do x in exactly the same way?"