The fact of the matter is that the two handed back hand is much easier to execute when compared to one handed.
Both have their advantages (2hbh- return of serve, High balls .etc. 1hbh- Lower balls, better reach, more maneuverable etc.) and disadvantages (2hbh- Low balls, reach etc. 1hbh- High balls, topspin return of serve).
I started using 1hbh when i first started playing tennis, but for most the 2hbh is much easier to execute and get good at.