I don’t think there’s a right answer to either of those questions.
I’m not entirely sure what you mean by systems management, but I’ll assume you talking about what I’d call systems administration.
Developers and Systems Admins would get roughly similar salaries, with sys admins getting a little more generally I think. I certainly don’t think it would be a good idea to pick one career over the other based on salary though.
I’d wager that it’s easier to get that kind of work in Ireland (or UK) than anywhere else in Europe, judging by the amount of foreign developers I’ve worked with in the past few years.
I’d also wager you’d get better money in Ireland or UK than anywhere else in Europe.
But hey, with the way our economy’s going, we could all be heading to china to find work in a couple of years ;)