What's often overlooked with PLBs is that you have to actively trigger them, whereas if you leave tracking active on InReach (or, I guess, SPOT - I only use InReach), then if you're lost without triggering the device, there is a last known location for SAR. Likely, there us a cluster of locations at similar points, showing you've been there a while. Thus if you're unconscious or unable to reach your device, there is still good data. With a PLB there is no data.
On the latest firmware, my InReach used <50% battery in 9 days, with 20 minute tracking and sending/receiving maybe 100 messages over the period. I'm confident that on tracking only, it would last 30 days.
Biggest plus of the InReach, for me, is the weather reports. A backcountry ranger asked me for the latest updates (amazingly, it turns out that their InReachs aren't able to use the WX2INREACH weather service!).
