I have a spectra and like it. Spectra (3/8 ths inch) has a tensile strength of 4,500 lb instead of 2,000 lb of poly. This makes it very useful for rapeling, z-draging, etc. Since you don't really want to exceed 10% of the rating in a rapel, you can't exceed 200 (wet and geared) on a poly line whereas you can go up to 450 lb on a spectra. It does have its downfalls however. Spectra melts really easily. If you use it for a z-drag you must keep it wet and move slowly. I once had a line melt from pulling on a slip knot. Also, it doesn't float as well so I've had some swimmers float right over it. Ideally, I would use a poly for throwing and a spectra for rigging but that is not practical so I use a spectra line for everything.
P.S. Get the longer rope, a shorter rope will eventually frustrate you.