Since you're in Colorado I'd recommend liners in the fall/winter and rubber in the spring/summer. Liners do a much better job with melting snow and thick mud. Rubber mats are more comfortable for one's feet- especially the driver's. The liners tend to curl a bit and get to be a bit annoying to the driver. The rubber ones fit more nicely all the time.
Weathertech and BMW liners are exactly alike except for different logos. I bought the the BMW rubber ones- and use the 2 season system.
2014 528ix M Sport. Space Gray/Mocha Brown Nappa Leather, Anthracite Wood Trim. Packages: ACC Stop & Go + Active Driving Assistant, Driver Assistance, Driver Assistance Plus, Lighting, Luxury & Premium. Options: Paddle Shifters, H-K. Surround Sound System, Heated FS's & Power Rear Shade with Manual SS's.
2013 X3 28i M Sport. Deep Sea Blue/Sand Beige Nevada Leather, FS Wood Trim, BMW Apps, HG Rails and GY LS All Seasons. Packages: Cold, Conv, DHP, Perform, Prem, Prem Sound and Tech.