You should be alright with Modo and 3dcoat. But it's your design skills that will matter more than what software you use when it comes to getting freelance gigs or getting studio jobs. Do you not know Vitaly Bulgarov and Alexey Pyatov aka Karanak, who use Softimage and Sketchup respectively, for their 3d concepts? In your…
I've never heard of a company wanting a concept artist that can also do 3d. If you really wanna be a concept artist, I would spend 100% of my time on it. Since it's super difficult. As for software recommendations. I would say use whatever is used in the industry. I know nothing about the film industry. But for games…