Go with a flatbar. First, if you get a drop bar you'll spend 95% of your time on the drops or hoods which is the equivalent of riding a flatbar. For a large person, sitting more upright will put less stress on your breathing. I don't buy the the "hand fatigue" argument against flatbars at all. I have a flatbar and riding 50-plus miles is no problem. In fact, I used ride drops but found the bar too narrow and that hurt my hands. Back then I never even considered a flatbar, but once I tried one, I never wan ted to go back. Get ergon type grips. You can add bar ends if you want more hand positions, but you can alter your hand positions even without bar ends. Flatbars allow you to sit up and you'll have better visibility which is a very good thing. Have fun.