My wife is training for a half marathon and has spent the last few weekends doing long runs to prepare. I decided to keep her company on yesterday's run, which led to the inevitable comparison of running versus cycling. Here it is by the numbers:
Running: shorts, socks, underwear, shirt. Total cost=$200. $250 if you're a woman and need a quality bra.
Cycling: shoes, bibs, socks, jersey, helmet, gloves, glasses. Total cost=$775. A little foam padding in the bibs makes them cost five times as much as a pair of running shorts and underwear even though they're made out of essentially the same materials.
Running: shoes. Total cost=$125. $250 if you also want a pair of trail running shoes.
Cycling: bicycle. Total cost=$4000. That much again if you also want a mountain bike. That much again if you also want a TT bike. Half that much again for a cross bike.
Running: watch. Total cost=$35-$400 depending on whether you want a Timex or a top-of-the-line Garmin.
Cycling: computer. Total cost=$50-$3000 depending on whether you want a wired Cateye or a top-of-the-line SRM. Multiply by number of bikes you own.
Running: you can run pretty much anywhere you can wear shoes. Want to run on a business trip? Pack some shoes and a pair of shorts in your carry-on.
Cycling: you need to find a suitable road/trail and a way to get there. Want to ride on a business trip? Either arrange for an expensive rental that will require an extensive dick dance to get it to almost fit or else purchase a very expensive travel box for your bike and be prepared to pay the equivalent of a second fare when you inevitably fail to convince the airline agent that it's a "trade show display."
Likelihood of desperately having to poop at some inopportune moment during any event of 90 minutes duration or greater:
Credit where credit is due to The Oatmeal for his similar comparison of the pros and cons of a man sitting down to pee.