It's not necessarily a contradiction but some sugars like fructose are absorbed more slowly. Complex carbs may be useful for long rides but useless for a two hour ride. Sugar free...as in...artificial sweetner with no calories is of course worthless. Do some research on the various gels and cross index some ingredients to learn a bit about how they vary and then try some different ones to see how you like them. On a one or two hour ride, simple sugars are probably about right for most people but not the best for long rides where you want energy delivered over time. Different folks react to these things uniquely so you'll simply have to try some things out and see what works for you. For one hour rides nothing is needed. For two hours almost any type of sugar will do if your body tolerates it.