Which servers are easier to deal with?

I suppose it depends where your experience lies.

I think you'll find if you come from a windows background that a windows server will be substantially easier to manage. As opposed to teaching yourself linux, in a production environment.

If you want to AUTOMATE scheduled maintenance and achieve ZERO downtime (don't fall for Microsoft's "Scheduled maintenance windows are not downtime" bull$#*^) then go with a *nix-based solution. If you like having to be encumbered by a GUI, scheduled downtime for maintenance, pay for per-user licensing IN ADDITION TO software licensing, etc. then by all means choose Windows.

Really, with a server, you have to focus on what you intend for the server to do. What application(s) it needs to run; what services it provides; what other systems it will need to interact with. From that, you determine which type of server fills those business requirements best.

I think that "license costs" should not be a major issue in the decision. And "support costs," whether they're your own employees, yourself, outside contractors or some combination of all three, are going to be fairly high anyway. What you need to do, on that score, is to carefully enumerate them.

It all depends on your level of experience. Windows is MUCH more expensive in the first place, but is very easy to maintain and set up. However, if you enjoy full-blown configuration and customization, then Linux would be a much better choice.

As sundialcvs pointed out, it depends on business requirements. If, for example, they intent is to run a legacy app built on asp.net and coded in VB (ugh!) then the correct solution would be Windows, because mono support for vb lies somewhere between immature and nonexistent.

Likewise, if they have chosen Microsoft CRM for their custom relationship management needs, then they will be definitely needing Exchange and SQL Server - or at minimum SBS and MSDE (don't try to run Exchange and SQL Server on the same box, even though SBS installs both. You WILL be in for a painfully slow experience).

TCO is generally lower with Linux than with Windows, when you actually take the full TCO into account, and don't selectively analyze it like Microsoft does, and shift numbers by redefining "downtime" to something different than the rest of the industry's definition.

Back when I was a little helpdesk minion the answer presented itself in the middle of the night. (Windows servers paged out problems 10x more than the unix servers).