Already said, but:

Even for web images, postwork is easier on a bigger image. Shrink it after. Works very well.

For print, render as big as you can stand. You can calculate to exact dimensions what you'll need, but then, sure enough, there's a decent chance that a year later, you'll wish it was just a bit bigger. This is especially true if you think you might ever sell your renders. Someone will want the exact image in your gallery, but they'll want it cropped a certain way and still maintain similar resolution, and you'll wish you had a bigger original.

If you don't do postwork, it's not as big of a deal, as you can always just save the PZ3 and re-render whenever you want.

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.