I wouldn't want the SG280 as my only one. I put a ton of time into dreaming up the tree-mek. I think I found the perfect balance between length & weight of truck, reach & capacity of crane, and size & weight of grapplesaw for my particular area and types of trees. I wanted a small, maneuverable unit that I could get into yards and tight spots. The trees in my area are deciduous, mostly, and average height is 75'. I can handle trees up to 115' though.
So is mine a mini version of a PK40/SG280? Yes and for many good reasons.
It all comes down to what you need for the area you work in.
Keep in mind, a bigger crane means longer truck, heavier unit overall, wider outrigger span, heavy vehicle tax, apportioned plates, higher registration, and less access. The trade off is more capacity and a little more reach.
It's your call. Just a few pointers to help you decide.