When a group of friends did the Leadville 100 (mountain bike) last year, we tested a few options so we could track their progress and be ready for them at the pits . It was also for all the family and friends back home to get live updates from the course.
One of the guys had a SPOT and we tried the GTU 10. The GTU 10 was way more accurate and timely in displaying their location. We created geofences before and after each of the checkpoints and would get email/text alerts within a few seconds of them crossing the "fence." The SPOT was much slower to give an update, so by the time the screen showed their location, it was at least five minutes later. This may not make much of a difference for your purposes, but for us, we needed it to be as precise as possible.
We did testing during their training rides and came to the conclusion that the GTU was the clear winner. Since the SPOT was fine for a backup, they just took both devices for the race. It was interesting to see the comparison of the maps after the race.
While the battery life is stated to be one day to one month, it really depends on how often you will need to have pins dropped. I think it lasted for a couple of weeks of training rides.
And, as you know, this uses AT&T for the service. So, if you will be outside of cell phone coverage, this may not work for you. Also, it definitely held more than the last 10 points of history, I never counted them, but I'd say at least hundreds, if not thousands.