Hi Bob...
Everything you've said in your post is correct. The dirt bucket, I believe, is JD's standard bucket. It is thinner gauge steel and will likely bend or warp if you knock it around a bit carrying or pushing rock or other heavy debris material. Yes, it also is easier to weld bucket hooks on JD's heavy duty bucket because of the reinforced upper lip of the bucket. Otherwise, the dealer would likely have to first weld a reinforcing strip across the upper lip and then the bucket hooks. Buying the heavy duty bucket with pre-drilled holes is a good choice. You can carry rock and not be concerned much with dents or bending. Also, you can replace that cutting edge whenever needed since it can quickly be removed.
Regarding the standard bucket, I personnally would buy JD's larger heavy volume bucket. This is just like the standard bucket but is much larger and will accommodate larger volume loads of lighter material like snow, hay, sand, etc. I could have used this bucket this past winter with all the snow we had around my place.
The forks also are a good investment. You may not use them all that much in any given year but when you do they are sure handy to have around. I've been able to move around larger size boulders with these forks that I couldn't move with my HD bucket due to the boulder's bulk.
...Bob