I just finished a 4 1/2-hour ride on my 19-pound track bike (48/18 gearing) in Baltimore County and Carroll County (very hilly terrain). I'm thoroughly wiped out. Last month, I did the same ride on my 34-pound hybrid bike (triple chainrings, 7 sprockets). Much, much easier ride.
Just reinforcing the point made above by BlazingPedals:
"No matter how you look at it, the difference in workouts is YOU not the bike."