This is a tough one. There is a point early in the season when I have been running outside but riding indoors that running up the hills actually feels easier. But... after I build outdoor and hill endurance on the bike, they start to even out, and then I think riding up hills might actually be easier than running up them.

With either one, it seems the only way to get better is to just do more of it... I get sick of running a lot sooner than riding, so maybe that's why riding comes out easier in the end