Based on this paper

2015, Simulation Tools for Model-Based Robotics: Comparison of Bullet, Havok, MuJoCo, ODE and PhysX, https://homes.cs.washington.edu/~todorov/papers/ErezICRA15.pdf

It seems MuJoCo is the best, around 2015.

Now?

Official Documents about modeling: http://www.mujoco.org/book/modeling.html

A simple tutorial shows it is not too impossible to master it quickly.

This python MJCF XML file generator seems can simplify the modeling a lot. Possibliy eliminate writing `XML` details by hand.