Quality and conscience are key for me. The mainstream platforms deliver good image quality, fully translated subtitles, carefully curated content, and even extras like interviews and fully restored cuts of films. Sites like filmygod.com are good for surprises like finding very rare films or local stuff that mainstream services haven’t yet put online for various reasons. Films by obscure directors for example that for whatever reason have not yet been digitized by mainstream services.
On the other hand, mainstream websites put a lot of work into preserving editions of movies and providing context to them, such as providing restored versions of a movie, complete cast and crew lists, and even curating lists of movies based on a theme or the films of a particular director. All of this adds a lot of value to the movies they provide and really helps to enhance one’s appreciation for them. This is why I prefer to use aggregator websites like filmygod.com as a last resort to find obscure movies and then try to seek out and purchase or rent those movies through legitimate channels. It’s just easier on my conscience that way.