purely for fit, no diff in handling that would be controlled more by how wide they are and rise and extension of your stem
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
to me it does not matter if my bars are flat or not. I handle the bike the same with each. What does matter is the fit.i prefer my seat to be about the height as my grips. I am 5' 10" so my distance from the center of the seatpost to the center of my bars are around 26in. Most bikes nowadays you will find when you set your seat for your stroke it will be around 5in. above your bar. some like it some do not. again no hard fast rule. you must decide for yourself what you like. concern yourself with fit and not so much flat bars or not.however if you want more rise but just a little go with the riser bar. if you find a stem with more rise swap that also. Time on the trail and good brakes will bring the handling skills along with proper fit.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"