I bought my Spot X (non-Bluetooth) because I wanted the ability to send and receive messages in the event of an emergency.
With the standard Spot units, you can hit the Check-In button (which will send a generic "I'm fine" message to the people you set up in your account), or you can hit the SOS button in an emergency. The downside to the standard units is that there's no way to verify that your message was received.
With my Spot X, I can have up to 14 pre-defined (i.e. pre-written) text-type messages pre-programmed, and can send an unlimited amount of those. So in my case, I set them up in my account to say different kinds of messages, and can send those different messages to different people directly from my unit. If I want to hand-type a custom message, it costs me 25 cents per message (and my package allows 250 per year).
The benefit to my Spot X is that if I send a message out, I can receive a confirmation back to me (in the form of a response from that person). That way, I know the message was received. It may be a small item, but I'm sometimes in areas where I have no cell coverage. Being able to get a message out - and have it conformed that it was received - is worth the expense for the peace of mind.
You'll have to decide what your priorities are with regard to communication. Cell service is not 100% reliable in 100% of the country, so you pays your money and you takes your chances.