I own both. Either will do the job, it's hard to go wrong.
16mp vs 20mp sensor makes no difference. I use them interchangeably, I don't notice any difference. You can make a slightly bigger print... big whoop
E-M1 is weather-sealed, has a built-in grip, excellent ergonomics, slightly better C-AF. It's better for larger lenses, tilt screen. There may still be superb deal on the E-M1 + 12-40mm ($1200), I don't expect that to last. If he's looking at zooms, that alone makes E-M1 a no-brainer.
The Pen-F is a bit more about style rather than substance. If you like the retro style, it's insanely great, the build quality is stupendous, the feel of the dials is superb. The EVF is smaller, I prefer it because that makes it a tad crisper. It has a FAS.
Pen-F JPEG dial, well... It can be simple if you just want to turn one dial and get punchy B&W JPEGs or the Art Filters. You can also tune the dial settings if you're a total nerd and can figure out the interface, but it's still not as versatile as RAW.
The only other thing the Pen-F has that E-M1 does not is high-res mode. Since you need to use a solid tripod and a totally static subject, it is highly unlikely he'd really use it.
I normally use the E-M1 with the battery grip for landscapes. The Pen-F is for casual use, city stuff, the rare occasion when I opt for high-res, and as a backup body.