Bumping this, because while I don't doubt the above answer is absolutely true in the slightest, it really doesn't help me when I'm not sure about basic functionality of 5CP.
By that I mean, with an A/D map you obviously know how much significance each point should have - with each point progressively getting harder to attack.
But take the second point in a 5CP map. Since either BLU or RED could control the BLU spire at any time, who should have the advantage?
All I've been able to gather is that generally second points should be able to be held, but once they're taken the attacking team then have the advantage, and this is reflected in the design where the point is usually on a high vantage or good defensive position, but has a low ground where defenders will be pushed back to and last when it gets taken over.
And then when it comes to mid points I just can't make an interesting layout without looking at it closely and realising I'm just copying am existing map (usually Badlands).
My point is, none of my knowledge about the mode is concrete, and it would be nice to know if there is any guidance on this sort of stuff, or if anyone has any knowledge they'd be willing to share about it.