I think the only risk of 32GB not being enough for most people is when they go on Vacation and shoot HD quality video and lots of photos... It seems like a ton, but when you are shooting about 75MB per min, that works out to be 4.5GB per hour... So, for that Disney Vacation that lasts a week, you get about an hour of video a day plus some photos before that 32GB is packed. Then you have to factor in that you probably have some music, movies and other media on there as well.
32GB is a ton of space, but it fills up quicker than you think with the quality of the recordings on the 810... The guaranteed 64GB capacity of the 521 makes it a bit better deal - if you don't mind losing a touch of resolution on the camera and the flash. The processor doesn't lag at all, the lower memory can create some strain when running heavy games, but isn't a deal breaker. I think I'd be inclined to grab a new 521 over the 810.