besides the obvious what it the difference when it comes to brewing?
In terms of effect on the beer, not much if anything. In terms of usage, it kinda depends on your system. For one of my kettles, I need to bag whole hops, but pellets can go in loose. For the other one, both need to be bagged. For some people, neither need bagging.
I also need to bag my whole hops as not to clog up in my system, but pellet hops can be boiled loose. I prefer whole hops over pellet hops. Not too sure if there is any significant difference between the two, but I believe whole hops are less oxidized due to processing of pellets.
I prefer whole hops - pellets clog my screen. However, you can expect a higher alpha acid utilization from pellets because the lupulin glands are ruptured in the pelletizing process. Also, if you’re making a big beer with lots of hops and you’re using whole hops, you will lose some liquid as it is absorbed by the flowers. So plan accordingly (i.e. when making a double IPA, plan for 7 gal vs 5)
If you have absolutely guaranteed fresh whole hops, I agree. But in general I find pellets store better and stay fresher longer. I always buy continental hops as pellets.
Unless one knows the hop farmer, it’s hard to do that, but I’ve started growing my own. I don’t get quite enough yield to be self-sufficient yet so I buy from hop direct or fresh hops. I recently (last November) ordered some Centennial and Cascade hops from hops direct that were the freshest I have ever purchased. I mean they were a brighter green color and outstanding aroma. I am very pleased with them.
I vacuum seal and freeze my hops.
I use both whole and pellet. I agree with Denny for Continental hops - I prefer pellets for freshness. Not saying you can’t get good leaf hops that are Continental. Recently I have been buying more pellet hops though. Easier storage and very easy to use on my system. Leaf hops also work on my system quite well.
Around here, it’s not as hard as in other places. I call Dave Wills at Freshops, find out when he’s picking up hops from the farmers, and order then!
Nice Denny. Could you let us know when that happens this fall.
I use mostly pellet hops, mainly because I buy hops in bulk and the storage space needed is much smaller with pellets.
It actually happens several times, depending on variety and source.
I prefer pellets becuase they are easier to use and won’t clog my WP chiller. But I have a ketttle I use specifically for whole hops.
I do like the ease of using pellets. They’re easier to store and easier to weigh plus you don’t need any bags. Alot of advantages with pellets.
I also use pallet hops most of the time.
If I use whole hops I have to use a bag as they would not plug my pump.
I prefer whole hops. They provide something solid for all the hot break to get stuck to.
Equally important, I have an older (kinda rube goldberg) counter flow system with a 1/4" outlet. Whole hops are screened out upstream, but pellets can make a muck that can clog the line if the flow is too slow.
It sounds bad but works pretty well in that I get good oxygenation during the slow run-out. 
I prefer whole hops - simply b/c I need the filter bed or my screen gets all clogged up.