The spray foam is FANTASTIC! It is more expensive than fiberglass batts, but WELL worth the cost difference. I am a home builder, and we used to use it at my last employer. There are a few benefits over batts...
1. No air space at all. It insulates better than the same thickness of fiberglass.
2. Bug resistant (good for under houses). It has a chemical in it that bugs (especially termites) do not find yummy.
3. Does not compress over time causing the need to replace or add more.
4. Has a better flame spread rating that comparable fiberglass.
5. Acts as a better noise dampener than fiberglass.
Several years ago, I worked for a custom homebuilder and had a 4500 sq. ft. 2-story that was completed, waiting on the closing. It was in the middle of winter (that winter was actually COLD). The home was about 70% ceramic tile and stone which does NOT hold heat well. At the end of the day, I forgot to set the thermostat on the home. When I came into work the next morning, I was dreading walking into it without the heat on overnight. My heater at my personal home ran most of the night to keep it 70 degrees in my home, but when I walked into this home with the heater off overnight, it was over 70 degrees! The home had been insulated with the blown-in expandable bio-based insulation. I have been a true believer since then. The only reason all builders don't use it is because it is quite a bit more expensive than fiberglass batts.
One note of caution.... If you can do it yourself and decide to, WEAR A RESPIRATOR AND GOGGLES! That foam expands over 400%! Imagine running back in to do a minor touchup and not wanting to put your respirator back on. Now imagine that a chunk the size of a BB splatters while you're spraying it and it lands in your mouth. If it got into your throat, it would expand enough to cut off your airway before you could get it out.
DIY is great, but people don't realize how dangerous it can be to strike out on their own doing remodels sometimes.