Good question. There are things about that I don't understand from staring at geometry charts: the 26" bike has a longer wheelbase (huh?) and shorter fork length, but most of the frame/fork dimensions are either the same, or similar. The smaller wheels (even wearing the 1.75" tires) spin up quicker, and have a somewhat smaller rotational moment, making for quicker acceleration and nimbler handling. The hand-built wheels on the new bike are a little lighter, and the Chris King hubs make whatever difference they make, and supply entertaining sound effects when coasting. Differences in the cockpit geometry are noticeable: the handlebars are set lower on the little bike, and the handlebars themselves are somewhat wider. Taken together, these differences and others (drivetrain, for example) give the two siblings very different feel. I'm quite sure I don't really understand all of it, but I'm enjoying the variety.

Re tires and pressure: I'm running Compass 1.75" at 45/55 psi on the 26" bike, Compass Barlow Pass 38mm Extralights at 50/60 psi on the 700C. The 38mm tires are significantly more supple, and I prefer them in most cases. If Compass ever gets around to making an Extralight variant of their 26" tire (doubtful, for industrial engineering reasons, apparently), I'd spring for a pair. If they made one in 2", I'd wag my tail while writing the check.

Both bikes do well on both road and mixed terrain rides. The little bike is still new enough so that the longest ride I've taken on it (~50 miles) is only about half the longest ride I've taken on the big bike, but it convinced me that it's suitable for all-day use. With 10,000 miles on the old bike, I've got some powerful biases established in its favor, especially for long rides, but am having fun swapping off, with occasional forays on the old GT with its 55mm balloon tires completing the program.

rod