I think that WHDLoad is more useful on a real Amiga, because it's so easy to manage and switch virtual floppies (.adf files) in UAE. :-)
I have paid for WHDLoad myself, it's very comfortable not having to deal with floppy disks on my real Amiga, but I wouldn't have bought it if I only used UAE.
One could argue that it's strange to pay for hd installations for games which you already own, but the WHDLoad developers are doing it on their own spare time, and the registration fee isn't much.
By the way.. Do you want to get back into democoding? :-D