You will lose the 3.5 lbs of body fat faster on the 20 lb bike to make up the difference.

Back in the day when I was lighter and less sane. I took an old water bottle and filled it with lead BB's and epoxy resin. That was to weight down my light 20 lb bike to get stronger on training days.

My old coach used to say don't be afraid of the guy who races the 10k blah, blah. Be afraid of the guy riding a Huffy with some weird glow-in-the-dark liquid in his water bottles.

However, the 2 grand in cash must weigh atleast 1/2 lb. So the net weight difference is 4 lbs due to lighter pockets.