One thing that you'll soon discover with whoopies versus straps is that allow for a shorter minimum distance between trees. Straps can go virtually to the end of the hammock, whereas whoopies require space for the line and then the webbing. Another benefit to straps is that if you find yourself in finger-numbing cold, straps are easier to manage and adjust than whoopies. As far as keeping the straps from getting the hammock wet, the buckles or rings act as a water break.
I've found big trees to be an issue as well with whoopies. The tulip poplars in my backyard are over 8' in circumference as are many other in old growth forests around here. Having some 12-14' straps will manage that more easily than whoopies and 8' straps.
I have both straps and whoopies, but I've been reverting back to mostly straps due to their adaptability and ease of deployment.