One big difference is that because you don't have to dispose of so much carbon when you run on ketones rather than glucose, you don't produce so much CO2, hence you don't need to respire so hard.
Phinney tells both stories to Jimmy Moore in this podcast:
479: Legendary Low-Carb Researcher Dr. Steve Phinney Says There’s An ‘Art And Science’ To Living Low-Carb | The Livin La Vida Low-Carb Show
What Volek and Phinney make very clear in their book --
Amazon.com: The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-Saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable (9780983490708): Stephen D. Phinney, Jeff S. Volek: Books
-- is that you can do demanding activities on glucose or you can do them on ketones, but where you get stranded is if you're in-between. They say it's like thinking you could set off for a holiday island, but do just as well stopping half-way. However, you can't if there's only sea in between. I kind-of knew this, but they explain the whole phenomenon so well that I think it only really hit me after I read their explanation. The PB maintenance phase ("100-150 grams/day Primal Blueprint Maintenance Range") is low-carb but not ketotic, but of course Mark's not telling people to try cycling for 60 miles on that protocol. "Move slowly," huh?
The podcasts where computer guru Steve Gibson tells Leo Laporte about his experiments with VLC are interesting, too. Gibson, much to his surprise, found his work output on his stairmaster going up and up with less and less effort after he'd adapted to VLC:
TWiT Live Specials 124 | TWiT.TV
TWiT Live Specials 125 | TWiT.TV
Then there's the astounding physical endurance of the fur traders and voyageurs. All done on pemmican:
I have to say I've dabbled with low carb before, but never actually gone fully ketogenic. However, after reading V & P's book I've become very interested in the concept. It seems like something worth trying as an experiment. I would like to see if I could have the experience of tapping huge reserves of energy. I'm sure primitive people in high latitudes must have spent much of the year in this state, as has been said on Lights Out and many other places.
Nora Gedgaudas seems to do very well on a Paleo VLC diet:
Primal Body-Primal Mind | Beyond The Paleo Diet