I try and use leaf exclusively when I dry hop, but have started using it throughout my process.
I have noticed that my beers have a better flavor and smoothness to them with the leaf, and find that for the purpose of dry hopping, I do have to go a bit longer. I also dry hop at keg temps, so that could slow the process down. I will fill my kegs, toss in the leaf hops and carb it all at the same time. By the time it's carbed up, it's pretty well dry hopped, but I find going another week makes it even better.
Pellets work just as well, maybe slightly faster IMO, and with the added trouble of keeping them out of your finished glass of beer.