I'm in the process of figuring out my all grain setup. I'm thinking of a 3 tier gravity setup. I already have 2 kegs, one of them already converted to a keggle and was planning on using the other for the sparge water. I'm stuck on deciding if I want to go with a cooler or another keg for a mash tun. What are the positives/negatives of them? Does a converted keg lose heat faster than a cooler (seems like it would)?