One larger fan is always, well, almost always depending on the fan, better than two smaller fans. A single larger fan will flow the same or more air volume with a lower noise level and less turbulence than two fans will since it can do the same job at a lower RPM.
The 230mm version of the Bitfenix fan moves 156 CFM at max. The two 140mm fans together are only 146 CFM at max. Overall sound levels are likely similar at max.