Nearly all my 200+ hrs is in cessnas but I recently got checked out on the Cherokees for the reason cited above...to have more scheduling options at the FFBO. That paid off last week when we decided on short notice to take a 3day, 800nm round trip, and the Cherokee 180 was the only plane available. I about doubled my total time in the cherokee on the trip.
Sticking strictly to XC considerations, these are my observations:
1. If you are really into pilotage and dead reckoning, the high wing and higher seat of the 172 is better. If the view is not that important to you, then you can discount that.
2. Anything more than an hour in a 172 numbs my butt and back. This week I comfortably flew a 2 hr leg outbound. On the return there was a little get-home-itis so we flew 3.5 hrs. That was a little too long, but I can't imagine doing that in a 172.
3. One of the reasons we were anxious to get home was our departure was delayed while we tried to get frost and snow off the wings. If that had been a 172, I'd have been forced to wait longer for the sun to melt the frost resulting in a nighttime arrival which is below my personal minimums, or rationalizing that I had gotten 'enough' frost off to launch. Advantage to the Cherokee there.