I don't believe those foams, gels, and other things do much but take your money. There isnt much a pad can do that wool or wool fleece can't so. Getting a saddle that fits is more important.
At the endurance events I have seen plain wool fleece, or tucker coolback type fleece seems to be the most common. They wouldnt be if they didnt work. I use a Tucker Southwest topped fleece pad. I'd use the wool felt style if the made one that fit my saddle. The tucker coolbacks, woolbacks, and southwest topped are good pads and all $100 or less.