The first has a higher r-value, is cheaper, and is flat which may be nice when sleeping with another person. However, it's about twice as large as it doesn't fold when wrapping up. Now I'd like to take this on car camps, bike tours, and backpacking. It shouldn't be a problem on my bike as my previous pad is about the same size.
But when backpacking, would there be a significant disadvantage to taking the larger pad? I assume it would have to go on the outside of the pack. Would the smaller one reasonably fit in a pack? It's a pound heavier but I don't plan on going on week long hikes just yet. Is this just a question of whether I would prefer the comfort of a nice pad or the comfort of less clunky gear?