I have used both matched and mis-matched tires. However, my particular flavor of OCD demands that only the tread pattern is different. Brand, width, and color must be the same. Currently, I'm running a 44mm Tufo Thundero (rear)/Swampero (front) combination, and I'm very happy with the increased front-end traction for my local conditions. Previously I have run the same in 40mm, and Pirelli Cinturato H/M in 35mm and 40mm on a frame with more limited tire clearance than my current one. I will be trying out the new Maxxis Reavers (both front and rear) in the near future. If I'm not satisfied with the handling, I may try the Rambler on the front.