The Core is a joke. I have one. I also have a GSAR. The redeeming features of the core is that the compass works fairly well, and it shows dual time which is nice if you are overseas. So you can always take a glance and know what your family is doing back home when you can call them ect.
For me though I would stick to the JSAR or GSAR. Or get a Marathon m16 gmt BEZEL from west coast time. Thats a perfect compromise.
I have the core black/black, def like it but have some issues. Altim, barometer, temp aren't great, also depth gauge sucks. Compass is good like the dual time