After seeing it both ways I have one honest recommendation.... DUAL! I cannot stress this more. At very minimum, run dual screws and drive them both with a belt, like the Solsyva's do. I switched mine to dual motors and the X and could not believe the difference. Dual screws over a single offer so much more rigidity and accuracy. Looking into the laws of force and torque the math certainly back this claim up.
That being said, it is possible to run 1 screw. People have done, and some with good success. However, (and this is big) your potential for racking and problems goes thru the roof. Any looseness in your system will show up there on the ends of your gantry.
All my designs use dual drive. Your free to do your own, but this is my recommendation since you asked.