Going on a cross country trip solo to several NP's & NM's want something for safety on the trails. Would like the best bang for the buck. Thanks
Obtain paper maps as a first step. The National Geographic series concentrates on NPS areas and they are generally quite current with any recent changes. Check relevant NPS web sites for current conditions (some places are closed due to Covid-19). Pay attention to the weather and know your limits.
If you do all this, probably the InReach Mini will be unused baggage. It is a highly regarded unit. Just don't be like the group at Grand Canyon who triggered their PLB on three successive days for frivolous concerns. They were removed from the canyon forthwith and doubtless charged for the helicopter ride...
As a retired NPS hand, I am impelled to ask - What areas are you planning to visit?
I have the In-Reach Mini. I always have my mobile phone with me, so the bigger one seems unnecessary. I also use GaiaGPS to plan my route and print my paper map and can upload that to thr Garmin. Short story, if you're also carrying a mobile phone (to augment the small screen on the mini), I think the mini is awesome.
Keeping your cell phone on you and keeping it charged is you first defense...at least electronically. Coverage gets spotty and non existent in remote areas and in the backcountry but often you can find service on higher ground and a text message often can get through if there is at least some service.
An InReach or similar satellite device adds "out of cell service area" messaging and satellite tracking and are more rugged than a cell phone. Tracking is mostly useful if you have friends and family following along on your journey although it could be useful for providing prior movement if you go missing. Messaging is useful for sending ad hoc positions, interacting with friends and family or summoning help from Search and Rescue (SAR) if you are incapacitated or otherwise incapable of self rescue. The messaging allows you to interact with your would be rescuers for advice and options so you can cancel the request if necessary.
For InReach, you must create an account with Garmin to set up and manage your device. It requires an active subscription and is fairly expensive to setup and run although not as expensive as a cell phone. There are various service levels at increasing cost depending on your expected usage. You can suspend the service if you are not using it but you have to unsuspend it (ie pay) if you want to use it's emergency features at all. Unlike a cell phone 911 calls there is no free lunch for InReach "SOS" messages. However unlike 911 from a cell phone where you need to know your location to be sure you get your request to the right SAR area, the InReach SOS sends your location and should relay your SOS directly to the appropriate SAR.
Garmin provide a somewhat dated smart phone app you can used to control your device from your phone mostly useful for setting options and composing custom messages and synchronizing your tracks back to your garmin app when you have cell service. It has a fairly basic GPS mapping function. Other smart phone apps are better.
The nice thing about InReach devices are that they are self contained as far as the satellite tracking and messaging service is concerned and do not require your cell phone to use that function ...although it is easier to do so. Cell Phones are somewhat fragile and don't work well in the wet or cold.
For most people the Mini is the InReach to get assuming you also will use a SMART phone. The other models make on device messaging easier and have a longer battery life which might suite an impetuous day hiker. The Explorer+ adds maps which give you a backup if you are otherwise relying on your cell phone for that. Generally you must actively cache maps on your cell phone before you lose service. Personally I prefer a printed backup but sometimes that is not possible if you come across a trail you want to explore. The 66i and 700i have better mapping and are more fully functioned GPS units but for most I think they are overkill.
There are some other devices that use Iridium like InReach, (eg Zoleom, Bivystick ) that have different pricing models. As far as I know these require you to use your phone for messaging although they may have a SOS button.
SPOT has models similar to InReach but its coverage is not as good because it uses a different satellite system. I don't know how their pricing works.
There are also PLBs that are purely SOS devices. They generally have a single setup fee and do not require a subscription. Possibly there is an annual fee. These generally have a variety of ways to signal and some can act as a beacon allowing more local radio finding. These devices can be good if it is likely you will move after triggering an SOS...skiing, river travel, maybe biking.
The best bang for the buck depends on your needs and desires. Personally I like the InReach Mini because it is self contained, small and light, has a good battery life and provides peace of mind for those at home I probably would not have bought one but for that. If you are mostly exploring well traveled trails there are generally quite a few people about. The dangers of backcountry backpacking while real are probably statistically much less than say walking through a city or riding a bike on a public road. Most people that actually need rescuing are poorly equipped day hikers who bite off more than they can chew.
"Most people that actually need rescuing are poorly equipped day hikers who bite off more than they can chew."
Most of those I have encountered doing SAR fit this description rather well....Most of the rest were poorly equipped backpackers on poorly planned trips.