Love my spot. I never had to use/discharge my old epirb thankfully so I can't comment on it's performance. I replaced it with the spot 2 once the old epirb needed it's battery replaced due to age (older and heavier so I was always going to replace it vs the battery).
I guess that also raises the question how can we compare them. I'm not sure anyone has taken 27 if the same epirbs and a spot and fired them off at identical locations along the way to see if both worked during a long hike (i could be wrong though...costly experiment if its been done

I would imagine there are places deep in a dense valley where neither would work too.
I always make sure I fire off my we're safe messages or come pick me up messages from wherever I am to test out the spot. I've never had a message not send. So far I'm happy with my purchase but I certainly see the advantages/disadvantages of both. As we have a young family my hubby and I rarely get to walk together (ones at home with bubs) so the spot 2 suited us as it allows the solo walker to contact home.