MSI is the strength of the graphite used in the shaft (more or less), and the Tour 110 and 125 are lower torque, stiffer profiles and lower launching and spinning than the stock 95 Black and 110 Silver. The 125 Silver is made with much more expensive materials and is smoother than the 110 Silver, but more or less the same shaft. Unless you are a professional or someone with a really quick swing/tempo that wants smoothness with the stability the Rogue Silver series provides (and have the cash to spend), I would go with the standard Silver 110.