Bat first is probably the way to go considering this piece of info:
Used wicket for Black Caps World Cup semi | Stuff.co.nz
A used pitch is only going to get more and more difficult to bat on as the game progresses. ITSTL.
It's interesting they're going to use the same pitch as the one they played on against England. The perks of being a host nation, and it's no surprise they're going to do what they can to assist the spinners.
NZ's ability in playing the SL spinners will be key, that's nothing new. Reckon SL would take the scalps of Ryder, Taylor and B. McCullum for a combined total of 100 runs or fewer right now if they could, and that would put them in the box seat. Their approaches are going to be very interesting. Although India v Pakistan is the one that captivates the neutral more than this, if NZ turn up and perform, we could have a belter.
I sincerely hope they put in a better showing than England did, and we have a much more competitive match in the semi-final than SL did in their quarter-final.
We allowed the spinners to bowl at us, were reluctant to use our feet or to go over the top with any real conviction. NZ must do this to upset the rhythm of the SL spinners. Be more proactive than we were, rather than being content to push and prod around and hope they give you a bad ball, force them into it and put them under pressure. Easier said than done sure, but we didn't even try anything (unless you count Strauss' rather troubled innings and cross the line swipes against Dilshan).
I look forward to seeing NZ's batting plans, and also if SL go with Dilshan opening again (the bowling that is).
Best case, NZ bat first and put up a more than battling total, worse case NZ line-up get into a mess against the unorthodoxy of the SL spinners.