Your question is one I've given a lot of thought to myself. For me at the end of the day it came down to the level of investment required, and I didn't want to committ the capital to a dedicated tracked machine (in addition to or instead of my Massey 5445 and Kinghitter S2 expander- so 340 kg hammer with 1.8M drop).
I am also on the wrong side of 55, so the "wear and tear" on my frame of climbing off and on was a big factor for me.
After a lot of consideration I decided Mark Hibberd's approach using a mini-excavator was the right one for me. There are a few people doing this and they nearly all have a slightly different way utilizing the machine, my driver is a homebuilt vibratory unit with an integrated auger rather than a hammer like Mark's or Stephen Blairs - it suits me and the work I do but would not be for everyone. All this illustrates is that there are several ways of skinning the cat . . .
If you want something off the shelf (and customer perception comes into this as well, I know a lot of farmers who would laugh if I turned up with my Digger, but my lifestyle clients love it) then that also is important.
Cheers