Wayne, does that matter now? The 997 died, so he's getting something to replace it.....
Yes it matters if the two units are connected with the AS INTERLINK to share GPS data.
INTERLINK won't work with any new units or iPilot Link.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, 360, RC-1