I run and bike. I tend to mostly run. I run 40-50mpw now ramping up to 70-80mpw by September, in preparation for an October 6th marathon. I cycle for commuting and for fun. I tend to park the car on the weekends and do most of my traveling on the bike. I ride back and forth to work on the bike when it is not practical to run. My guess is that I do 50 to 100 mpw (depending on the week) on the bike. I don't have a cyclocomputer, so it is hard to tell how far I ride.

Running uses less equipment, but the equipment you do use is much more important. Cycling with an out of tune, old, heavy bike will make you slow and tired. Running in worn out shoes will lead to stress fractures and knee damage. You can cycle in a cotton shirt and baggy shorts, you will be uncomfortable. Try running 10 miles in a cotton shirt on a hot day, your nipples will be bleeding before the end of mile number 7.

I find that to compare running and cycling mileage in terms of perceived effort a 1:4 ratio of running to cycling miles works for me. Running elevates your heart rate more quickly than cycling (especially on hills). Obviously coasting is not possible when running. I find that when cycling, I pay much more attention to what is going on around me. When running, my focus tends to directed inward more (not totally, just more). This habit would be very dangerous in traffic at 20mph.

Running and cycling are different enough that they cannot be directly compared. You will probably get "more" out of doing the activity that you enjoy most, because you will probably do more of it.