"I'm hiking the CDT, so I liked the Core for the 'Storm Alarm', the digital compass and altimeter."
I presume this isn't your first dance then. The issue then becomes whether you have a stand-alone GPS or not for the trip. Not needed on PCT or AT, and there isn't even concensus on the CDT but I'm in the camp that says "take one". Even if you're pretty good with map and compass, you'll use a GPS on the CDT if you have one. Whether or not it "saves your life" it can certainly save some time/effort, and just make you a bit happier by giving confidence at times that you really are doing the right thing. I particularly appreciated mine a bit over a year ago when sudden onset of snow/sleet/etc in near white-out conditions made it damned difficult to navigate coming out of the south San Juans.
A gps chipset in a smartphone is plenty for the AT and PCT. On the CDT I particularly liked having a dedicated GPS because then I had a dedicated power source just for that, and spare lithium AAs are pretty light to carry.
In terms of digital compass: while I am a gadget type of guy, I'm old school enough to want an analog compass.
Storm alarm: you're walking in the weather, you'll get a good feel for the afternoon storms as the roll in. I, at least, wouldn't see a need for such. I just don't see it as accurate enough to help much with a "climb up and over that thing vs. hunker down low and wait" decision. FWIW, thunderstorms never stopped or slowed me much, i.e., I didn't personally encounter situations where I felt it was too dangerous to proceed (I certainly did experience quite a number of afternoon thunderstorm events of varying intensity).
IF you end up with a standalone GPS unit --- then an altitude watch is IMO less of an issue. Yes, you have to fire up the GPS to get that data, but I suspect that a fair number of times when you would even care that you would be inclined to do so.
To be clear, I'm not suggesting that my approach and attitude is universal (!), just what made sense to me on that trail.
Best of luck, and I hope you don't have a high snow year! :-)