I've usually used panniers for touring but have sometimes used the Bike Friday trailer system for one-way trips where I wanted to have the suitcase along for packing the bike at one or both ends of the tour. Both work fine, but I prefer to use panniers to reduce the total weight. I try to pack light and keep my camping gear and other touring luggage to about 20 lbs. The trailer adds a substantial amount to this which I prefer to avoid. Might well be different if I were planning on taking 40+ lbs. of touring gear along since then the trailer weight would be a smaller percentage