The piece with Audrey Hepburn is aimed at chic females who may have glamour prioritized above being outdoors, and value brand name goods over ones that would serve them better in the long run. Using Hepburn sub consciously grabs their attention, and her own words invite the reader into the world of R.E.I.
The piece with Jim Whittaker tells the story of R.E.I. He was their first full time employee and eventually became the CEO in the 1960's. He was also a leader, and an icon in the mountain climbing, and backpacking community that R.E.I. was born out of. This ad is targeted at younger, thrill seeking males, and his quote suits that well.