I have had Spot3 for several years now, so over time I got some idea of what to look for in a satellite communication device. I think the things I care about fall primarily into these categories:
- communication features
- tracking
- reliability
- size
- batteries
- cost of the plan
- cost of the device
- ease of use
In details:
Communication features
Spot3 has pretty limited functionality given only 3 buttons - Ok, Custom & Need Help. If I ever had any emergency I would not be able to communicate nature, severity & urgency of the emergency. inReach is clearly better in that department as I think it has functionality for pre-defined messages and ability to connect to a phone. While pairing with a phone is appealing it may not be that useful in certain types of situations like extremely cold weather. From the review it sounds like Zoleo's strong point is functionality available through the phone and without it the device may be comparable to Spot3.
Tracking
This is something that I use most. First of all my wife never cares where I hike, so in an emergency my track would give a lot of information to anyone who would go to look for me - "Where did I park?", "Which way I do the loop?", "How fast am I moving?" Also, if my emergency was sudden e.g. falling off a cliff or being attacked by an animal the tracking might be the only information available. According to the review Zoleo does not provide tracking, so I already know it's not for me.
Reliability
Spot3 is kind of weak in this department. I often see gaps in reported locations and accuracy has been questionable quite a few times although it seems to have gotten better recently. People who own inReach seem to be pretty happy when it comes to reliability - perhaps the satellite system that Garmin uses has better coverage than what Spot relies on. I guess Zoleo does not have much track record here yet.
Batteries
I love the fact that I can replace batteries on Spot3 - it really makes it self-serviceable. Build-in batteries, no matter how great at the beginning always tend to degrade over time. Also I really want the batteries to last well over a week. My backpacking trips are usually less than a week, so I would want to have a buffer of at least few days on top of that. inReach seems weaker in that category. I guess this could be remediated by external backup battery but you better hope that this charging cable does not go bad during your backpacking trip. Zoleo seems to have a built-in battery, so I would put it in the same bucket as inReach.
Cost of the plan
Spot3 was pretty good at the beginning but then the cost of the plan & charges started to go up. At some point I just go fed up and discontinued the annual plan and I only pay when I have bigger hikes planned. Still I find it pretty expensive - most recently I had to pay around $60 to turn on the service for a month when my son needed it for a multi-day canoing trip. The thing is that any one of these devices can instantaneously become a lot more expensive to use with user having practically no control over this. What is a $4 monthly fee to keep the plan active today may turn into a $14 fee tomorrow. Also $20/month feels pricey to me. I guess only competition can keep the prices down.
Cost of the device
Perhaps cost of the device is the only reason why I haven't switched from Spot to inReach yet.
Ease of use
Spot3 device is pretty easy to use, however, I find the Web interface for managing the device really messy. I often get confused how to set up notifications and sharing and I just realized that with most recent Web site "improvements" I no long know how to export my tracks or how correct the time zone for displaying track points (it defaulted to Central Standard Time while I would prefer Eastern Standard Time.) I can't comment on the other devices.