I started out with a little electric 1.5HP Black and Decker
chipper / shredder. This worked great on my little 3000 sq ft lot in the trailer park. It could take up to 1" sticks.
When I moved to a house and a 15,000 sq ft lot, I moved up to a 5HP
chipper/shredder, the kind you find at Home Depot or Lowes. This was quite a step up from the little electric number, and suited my purposes just fine.
I then moved to my current place where I have 5 acres, 4 of them wooded. The 5HP
chipper/shredder did an OK job, but it was slow going. I upgraded to an 8HP Duer commercial duty
chipper/shredder, and this was a nice improvement. However, it was still slow, and even if you were only feeding it 1.5" branches (could take up to 3"), whenever you came to a "Y", you'd have to either force it in or bust apart the "Y". Putting the little branches (up to 1/2") in the top worked great, and I got some really fine mulch out of it.
Trying to run leaves through the
chipper/shredder was an exercise in futility -- it would plug up in no time, and then you'd have to take apart the grate and clean it out. This would waste the better part of an hour.
I finally upgraded to a 25HP
chipper with a 6"x8" opening. No shredding capabilities. I don't miss the shredding portion -- I just stack the leaves where the garden goes, and till them into the soil in the spring. Much easier. I don't think you could pay me to go back to one of those 5, 8, or even 10hp chippers. What used to take me 8 hours to chip up can now be done in 30 minutes. Night and day difference.
One problem with the 25HP
chipper is that it weighs 1600lbs and can be a pain to move around. I've seriously considered selling it to buy one that attaches to my tractor simply because it seems whenever I'm using it I leave it attached to my tractor anyway.
Here's a photo of my current
chipper (minus the engine, which I just replaced).
http://lh3.ggpht.com/_bVGGTY5HGmY/SUm7KYWcsvI/AAAAAAAADV8/GsJNQSGwSaI/s128/IMG_4069.JPG