mIRC scripting is a lot easier to learn, yes. But once you know another langauge it's really no harder to use that language than mIRCscript. There are already dozens of pre-existing IRC frameworks and basic IRC bots available for languages like the ones I listed above, making them as easy as mIRC when it comes to making a 24/7 bot.
Running a mIRC bot is fine for a small channel or two. But, if it's running on a dozen channels or more and doing some heavy duty stuff (real-time statistics, protection, etc.) then mIRC just won't cut it either because the script won't be able to take it or the connection (assuming we're on someone's regular DSL/cable line) which start to fail. Plus it means that person can't use their connection for much else. If we're talking about hosting on a remote Windows server then I would imagine it would be as expensive if not more so (especially one that allows you to run mIRC on it) than a simple shell account, which means you might aswell use a more 'appropriate' language anyway.
