It's up to you. Tecnomatix Process Simulate is modern and more intuitive.
If u are going to use Robcad or Process Simulate be aware that you need to have RCS module to modify programs, otherwise robot will not behave as in simulation.
On the other hand, you can use ABB RobotStudio which is preferable for simulating only ABB robots and modifing RAPID programs. You can get RobotStudio trial version for free.