I am a total noob! Not new to bikes but new to forums. My wife and I have been riding bikes for a number of years on rail trails and hard-pack with some hills. We have been doing alot of riding now in urban areas. My wife and I both are in our 50's so our riding is not extremely aggressive. The bikes we have been riding are mountain bike build ups that I have done myself. They have performed well, but I am geting the itch to build some new bikes that will be better suited to our riding. My research has taken me to a point that I need some help with. I plan on building up an aluminum cyclo-cross frame with a solid carbon fiber fork that will receive a mountain style stem. But I am not certain about the gearing. I have looked at the good old derailleur system but am also reading alot about the inner hub gearing systems including the newer CVP types. Any opinions on these systems? does anyone out there have a preference to a road set-up vs a mtb set-up for riding both rail trails and pavement with some hills, but not often?