They each have a few features the other doesn't, but it most definitely is the fact that people find that which they are familiar with easy and that which they are not familiar with difficult. It's not that one is actually more difficult than the other.
This is true of just about any SW packages - Unitrunker vs PRO96COM, Win96 vs PSRedit (although those two are very close in format), Kenwood vs Icom vs Yaesu, Wouxun vs Anytone vs Baofeng, Etc.
If you don't know the SW, it's poorly written. If you know it, it's the best thing since sliced bread, and very intuitive.