I will be riding in two charity rides this spring. One is a 20 miler for Tour de Cure for diabetes and the other is a 46 miler Tour de Toad for literacy in Central Arkansas. I have a hybrid and a road bike. I feel more control on the hybrid which seems would be better in a crowd but can obviously keep up better on the road bike. Terrain on the longer one might have a few more hills but nothing major. The first one is flat. Which bike would you ride and why?

I ride the road bike on the road. With rides like these there's usually a window of time in which you depart rather than rolling all together in one big group. And even so, there will be a wide range of capabilities, motivation and speeds and everybody will soon be strung out riding alone or in small groups. Some faster experienced riders may form pace lines with acquaintances, but that's not your concern. And though you may feel more in control on your hybrid, you might note that experienced roadies riding in packs and pace lines all ride road bikes.

Place interrupter brakes on the road bike and cruise on it whenever you want, just like on the hybrid!

Now those look interesting. I'll have to look into that. My skill level does not earn me a spot in a pace line at this point so It will probly be the hybrid. I actually think the road bike may exceed my skill and fitness level by a notch right now anyway. I only bought it because it was a good deal and it was pretty I do like riding it I just have a tendency to ride to fast so I wear out to quickly.

Don't sweat it. Just do the rides on either bike. You'll find everybody to supportive and helpful. That's the point. It's not a competition.

whichever bike you are more comfortable on

of course
if you have six weeks of training to do before the rides
whichever bike you train on will likely be the one that is more comfortable
provided it fits you ok
and the tires are properly inflated

I'd ride the hybrid if it's the more comfortable one. These distances aren't far and you could speed up the hybrid by putting more road friendly tires on it.

But don't you have to ride a road bike to be cool ?

If that's what you think, then ride the road bike. But some of the old guys like me think that the cool bikes are steel with great lug work and nice chromed head lugs.

IMO, either one will be fine for you if the fit equally well.

Chose the best tool for the job at hand. IMO the road bike would be better for the longer ride. You will not be in a crowd, and then the road bike is just that for the road.

In my own case I have a LWB recumbent and a trike. When I do club rides out on the hi-ways the LWB goes. If it is a club ride around town for pie or coffee rides the trike goes. Also the trike goes if it is really windy since it is more aero. Just use the best tool for the job.

Post pics of each bike. What gears does each have?.. how many miles have you ridden each bike?