Where about is the start of this trail? thanks in advance.

As a consumer.. to me it all comes down to price, quality, and availability of the product. I find no real difference in price of brand name products carried by MEC and my LBS until end of season sales or preseason sales at the LBS. However, what I have noticed is the quality of MEC brand products has improved over the years. If you think about it you will go in looking for that deal on a brand name item only to find a MEC product that is just as good and a bit cheaper. In my opinion my LBS has nothing to fear that a brand they carry will be also in MEC, but that the MEC brand maybe an equal replacement for that brand. ps.. 90% of the time I end up at my LBS for things I need anyway.

Sorry the 7 was to be an and symbol.

as part of the overall bike, a riders center of mass lined up with bike frame center is what gives the best control over the bike. to far forward traction is lost in the back. to far back and steering control is lost. proper frame fit gets the rider more aligned with the frame and gets the most out of the frame's geometry. for the car eg think formula 1 racer engin 7 driver very centered in car frame giving better control.