If you have never tried using different hardness grades, just find an art supply shop with a display of drawing pencils and try a little scribble with each grade. Note that since every brand is a bit different, you can't use your experience with one to exactly predict the quality of another, even more so when comparing wood-cased with mechanical pencil leads.

As for MPs, if you really get into it, you could end up with many different ones for different situations, sort of like with paint brushes or golf clubs. Even cheap ones can be comfortable and durable. Some people like the Rotring because of the heft, but they are a bit sharp and the weight can get tiring, rather like with using metal polyhedral dice.