Can o’worms……in short
Gels, chews, and to some extent chocolate offer quick release carbs – downside with chocolate is there is a good dose of saturated fat also (arind 30-40% in your average choccie bar).
Bars / oats / malt loaf / flapjack (home made) / sandwiches / rolls etc tend to provide energy over a sustained period and good for longer rides / all day type stuff.
Problem with sugar based energy is the spike it causes in your energy levels – look at the pro’s – they are not taking gels on until the end of the ride / race and are having sandwiches, bars, small brioce/buns etc during the race.
I don’t know if hydration means chocolate abosrbs better than a gel – doubt it as overall hydration does effect energy abosrbtion and levels – have you thought about using an energy drink instead?