Comment by PieterH

Fructose and sucrose are chemically identical (as in, the same) except that sucrose has an extra glucose attached, which breaks off in the stomach. Fructose tends to come in fruit, surrounded by fibre, which arguably reduces its cost to our bodies. Arguably, I say, because modern fruit is so extremely high in fructose, and because the sugar then hits the lower intestine where it messes up your bioflora, which affects your immune system and so on.