From what I've seen/read, 1 oz of whole/leaf hops == 0.85 oz of pellet hops in strength (I think this is due to the ground up hops in the pellets having a higher surface area).
Pellets will store longer and are more compact, but whole/leaf hops sure are a hell of a lot cooler, IMHO. I prefer whole hops over pellets for dry hopping use, but for boiling??? Makes no difference to me.
I'm sure some debate will start over which is better and why, but as far as I am concerned, there isn't a huge difference in the end.
The whole hops seem to be better suited for bagging during the boil (put them in a nylong drawstring bag). Then you can simply remove the bag at the end of the boil and you won't have to worry about clogging anything up.
Pellets seem (to me) to allow a lot of hop particles to get through the bag, and they end up floating free in the wort. Doesn't bother me too much, but if yoe are concerned with clogs....
-walker