don't get levers if you have cats or dogs, they get good at opening the door.

Levers are easier to operate. If you prefer a more contemporary look, levers are likely a better choice or a spherical design (Schlage Orbit, for example). If you prefer something more traditional, knobs are probably the way to go. I think it is accurate to say that most contemporary high-end homes designed today use levers.

Trend, schmend. Use what you like.