For me it goes as follows:
~28 liters for day climbs all seasons and light overnights in the summer. Serratus Genie with 3/5 of a 3/4 length Z Rest pad folded up as the 'frame'.
45 liter pack for multi-day alpine trips in the winter. Black Diamond Shadow.
40+ liter pack for multi-day alpine trips in the summer. Montbell Balance Light 40. Although the BD and Montbell packs have very similar volumes, the BD has a beefier suspension and padded hip belt and has more features including a crampon patch with straps and a bungee on the top lid, allowing more stuff to be lashed to the outside. It also carries weight better, albeit at a small weight penalty.
~75 liter pack for Alaskan climbs including Denali as well as long, technical winter climbs in the lower 48 (i.e. > 3-4 days). McHale SARC, custom built with light materials, very simple hip belt, no extra zippers, etc. Although a similar volume to the Wild Things Andinista or the CCW Chaos, you can actually fill it up and still carry it very comfortably and it climbs better than either of the other packs in my experience, although at a pound or so weight penalty.
For Denali, bear in mind you will be pulling a sled and/or doing double carries. No need for such a huge pack. I typically carried between 45 and 50 pounds on Denali and pulled about the same, maybe more.