I haven't done the Llanberis path but I believe it's the easiest and straightest path but not the best for scenery. I think the train goes up that way.
I've done the pyg and miners paths and they go past the lakes on the way up so the scenery is superb and it changes as you go up. The difficulty is getting a space in the car park at the start for those 2 paths.
Whichever way you go, the view from the top is amazing if it's clear.