Antialiasing is not a throwback to the 1980s that doesn't apply anymore. On the contrary, it is extremely important in obtaining smooth edges and diagonals in renders. It's also of critical importance when it comes to clean alpha channels and compositing. It has nothing to do with auto smoothing of objects, such as that which Poser performs.

Dpi has nothing to do with antialiasing, or file size, or render time. This is one of those "facts" that keep getting passed around the Internet and only confuse people. Dpi is only relevant when printing. It does not affect how an image looks on screen or how long the render takes.