I ran a test here using Callcentric.
Monitor Trace:
811903mS SIP Call Rx: 17
INVITE sip:17772345678.168.1.26:5060;transport=udp SIP/2.0
v: SIP/2.0/UDP 204.11.192.162:5080;branch=z9hG4bK-3d447fffeb4d2625be57a3f2f89e5609
f: "Jim Jones" <sip:17772401234@callcentric.com>;tag=15675 <<<<<<<<<<<<---------------- Note: f=from (AKA CLI)
t: <sip:17772345678@callcentric.com>
I created 2 Incoming Call Routes, one with just 17772345678 and another with 17772345678 plus 17772341234 as the "Incoming CLI"
I set each route to a different destination.
I called 17772345678 from 17772401234 and it routed to the destination I set for its "Incoming CLI" (17772401234)
and the LCD on the phone showed 17772401234
I called 17772345678 from a different number and it routed to the NON-CLI destination.
Based on my limited, Callcentric tests, I would say to use the number that appears in the LCD of the phone.
PS. Make sure both routes are using the same Line Group ID number.