Julien, that's the whole point with software. You need to try what's out there and find something you like and can afford. None of us can tell you the "best" one because we all have different needs and budgets.
Forget smoke machines. They are expensive, the smoke doesn't look realistic, especially for a diesel, and the oil that's used to create the smoke (usually some form of mineral oil), leaves a film of crud all over your tracks and the rest of the layout. A well maintained C-44 might have some smoke on start up but it shouldn't be constantly putting out smoke like a steam locomotive.
Forget smoke machines. They are expensive, the smoke doesn't look realistic, especially for a diesel, and the oil that's used to create the smoke (usually some form of mineral oil), leaves a film of crud all over your tracks and the rest of the layout. A well maintained C-44 might have some smoke on start up but it shouldn't be constantly putting out smoke like a steam locomotive.