The SSD drives are more resistant against impacts, as opposed to normal HDD's. If you expect to be pretty rough with your laptop, then get a SSD.

The normal HDD offers are far better bang-for-the-buck. You can get the 2.5" flavour or the normal 3.5" flavour. The 2.5" ones cost a bit more and their capacities aren't as large.

As for cost, check your local computer stores or ask your IT guy where he "gets his stuff". IMO, those quoted prices for Costco are far too high compared to specialty computer stores.

One more word of warning. I don't know how old your laptop is but does it have at least USB2.0? If not, it's going to be slower than molasses.