I've used avgas for 6 years now. I've learned a thing or two along the way....
Avgas is low lead, not unleaded. Spark plug will need cleaning every 10 gallons or so....about 120 flights of 15 minutes each for a 30cc class engine.
The correct mixture for the application will result in no significant gunk build up in the head and piston. Squeeky clean inside after 40 hours of operation
Avgas does NOT result in more engine power. Higher Octane number does not mean more power without engine modifications.
Premium autogas produces slightly more power than Avgas. (will turn the same prop at a couple 100 R's higher at full throttle)
Storage and shelf life is measured in years. I'm burning off the last of the 5 gal jug I filled two summers ago. There have been zero changes required.
No significant smell; whatever little there is, is actually pleasant
Current pricing puts Avgas at about 4$ at my local muny airport. Cheap, cheap but not as cheap as auto gas. To me that's the least of the concerns with gasoline
And last but not least, Avgas works great in our small mills. But do watch out for plug build up. The engine will run erratically (if at all) if the plug has bridged its element

Let me suggest you tell your friend to use an appropriate tuned system if he wants to race his gassie. A tuned pipe really extracts considerably more output from any of our small mills.

Glow fuel has both methanol and nitro methane, both of which add oxygen to the mix. Of course, glow fuel is burned at a rate of about 2 to 1 or more compared to gas which has advantages over gas. Nothing makes horsepower like timed ignition and "glow fuel", displacement for displacement. Dragsters are the epitomy of max output for a given displacement (mostly if not pure nitro methane).