any insight about this?
I’d lean towards size M (490), especially if he prefers a more responsive, sporty feel.
These bikes tend to run a bit long, and size L (520) can feel quite stretched unless he has a longer torso or specifically wants a more stable, relaxed position.
If he’s between sizes:
• M → more agile, more “in the bike” feeling
• L → more stable, but less lively
It’s also easier to make a slightly smaller frame work (e.g. with a longer stem or more spacers) than the other way around.
Also important to consider his saddle height:
If he has a relatively low saddle height, the smaller size usually works better because you stay more centered over the bike.
If he prefers a racier, road-like position → definitely go with M 👍