Swedish pro rider Emil Lindgren rides a size small Giant. Last summer he switched from the “XTC Composite” to the “XTC Advanced SL”. The difference between the two frames is similar to the Specialized Stumpjumper 29er coming in a standard carbon and “S-Works” version, but while the Big S uses essentially the same mould for both, Giant’s “Advanced SL” uses a different mould in addition to the stiffer, lighter carbon layup. The Advanced uses a chainstay mounted rear disc brake caliper, which allows the seatstays to be whittled down almost pencil thin for better compliance and weight reduction; for similar reasons, Giant reduced the diameter of the seatpost back down to the older 27.2mm standard. But the one thing that Lindgren specifically pointed out was that the head tube was shorter for the same size compared to the “Composite” version. Giant beefed up the head tube support from the top and down tubes, allowing the overall length of the head tube to be reduced down to 90mm for the small (same as the small size Stumpjumpr). Lindgren remarked that geometry change improved his positioning.
The tall stack heights of the 29er front wheel and suspension fork mean that a lot of pro riders, especially the shorter ones, are slamming their stems (ie, running the stem without a spacer between it and the headset). Notice that Lindgren uses a slight negative rise stem, and he has either replaced the bearing cap of his headset or eliminated it altogether to lower his hand positiona few more millimeters. It’s kinda like the frame is being marginalized as the wheels have grown in size and importance.