0.7 at 7seconds is really really bad, you will need the 170 for sure.
We struggle when it’s under 2ft@7-8 seconds simply because it has to be so shallow for the wave to even break. I will stand on the side of the sandbar and catch a chip and pump into the channel then out the back but otherwise it’s thigh deep for it to break with that small of a swell.
I love both (obviously ) and find that my daily driver is the 170. In up to rib high surf I love the lines it draws and the benefit of the pump and easy cardio is huge benefit. After rib high or towing I’m on the 140. If you’re wanting to do some dw runs the 170 is a monster for its size. In the last week I’ve gotten 4 or 5 messages of guys setting new PRs on their first session on the 170 for distance.