I switched from FormZ. Took me maybe 2 months to be able to model anything, I am sure it will be faster for you. Did it for all the resourses and most of all to be able to handle very large projects, like city blocks with lots of trees.
I have used mental, octane, corona, and Vray. Vray took me a long time to learn compared to the others. But always come back to it becuase it is the best in quality and speed. I need a lot of speed and I don´t have the most powerfull computer in the world. I love using Corona, but for some scenes it is too slow. I recomend Octane only if you have more than one very powerful GPUs in your PC.