I put a pair of Schwalbe Marathons (not plus) on my commuter bike that I was repurposing as a tourer and I just hated the feel of the weight. I had Gatorskins in 26x1.25, t's a weird MTB size, and I think that's it, and these aren't much different than road bike tires, maybe a little heavier but not a lot. When my touring plans got canceled because of a torn meniscus I immediately put the gators back on. With the Marathons the bike felt like it was plodding along, with the Gatorskins it feels nimble, even with the weight in the bags.
Which brings me to a question, what other tires in a 26" size would you recommend for touring? I suppose I could just do a tour in Gatorskins too as they have protaction.