Is it better to have your drop parallel to the ground or slightly diagonal for touring? Or does it just depend on the riders preference?

Function over form always. Comfort and ergonomic preference while riding.

Which way do you like it better?

As Feynman wrote, "Why do you care what other people think?"

Best to have the angle of the drops match the most natural grasp of your hands. This is best determined while sitting on the saddle and some experimenting.

Brad

As I rarely used the Drops, for the vast Majority of the time, Touring. I have the tops of the Bars, to the brake lever hoods, level.

the drop's angle depends onthe way the bars were made. [ Bar end shift levers are there.]


that, amongst other preferences you choose for Yourself

Better for what?