#1 - Rock buckets- if your work deals with lots of big rocks then a bucket isn't useless. I'll admit that I have yet to hear of any folks here having such a dedicated need (never, however, say never

).
#2 - Protruding lower tines (that's what my EA grapple has) works for light roots and brush digging; as to the value of an "L" Bottom, "firewood" could be many things, same with "trees"- I've picked up massive tree trunks that would readily be grab-able was a clamshell grapple. If one has different tasks and only one tool then that one tool will have compromises.
#3. - If you grab up a bunch of brush a wider grapple is absolutely better. And, a wider grapple allows one to snag stuff to the periphery (of the wheels): I can more readily snag blackberry vines as I mow along- with a narrower grapple I'd have to push my wheels further into the brush (and if the blackberries are growing up/on a fence the wheels cannot go to far over else I'd be hitting the fence!). NOTE: I had my pallet forks on while mowing recently (I was combining tasks- picking up and dropping off my palletized firewood crates and mowing) and I was able to really snag some big blackberry vines (up in trees!).
#5 - A 3rd function is nice, but one has to justify the cost (how much is it really going to be used?). I plumbed hydraulics off my rear remotes; I use my full-detent ports as that allows me to just pop the control lever and the grapple opens or closes allowing me to more quickly free up my right hand (of course, I also have to pop the lever back into the neutral position as soon as the jaws get clamped down).
It's mentioned that dual lids are best. I'm not in total agreement. My grapple has a single lid and I have found no instance in which I have felt a dual lid would have performed the task signficantly better than a single: I've done things with a single lid that were likely better performed by a single than a double. I picked a single lid because it's less complex- only one set of hoses and one hydraulic cylinder to have issues with.