You probably don't want to hear my opinion, but...
I also have a Hunter 31, and one of my great joys is furling and packing my mainsail. It's easy enough to do and I get great satisfaction out of the appearance of a properly stowed mainsail. Consider saving your money or diverting it to some other area of your boat. As we all know, boats are loaded with opportunities to spend. We charter often in the Virgin Islands on larger boats and then it seems that lazyjacks are an absolute necessity, but on the H31, I'd rather spend my money on something really essential (like port and starboard icemakers). Of course, I am basically a weekend sailor in a northeastern climate, so I only sail perhaps 30-50 days per year. If your usage is higher, then I guess the convenience of lazyjacks outweighs the cost and windage factor. I hope this helps you decide what's best for you. I enjoy these posts because you always get a broad spectrum of responses. Whatever you decide, let us know.