I'm considering switching from a BA insulated air core pad to a foam pad to save weight. What's the most comfy foam pad of them all?

Closed cell or open cell / self inflator?

Closed cell

Probably the Thermarest stuff as the GG Nightlite is a bit hard comparably. But I live in the middle of gear hell without much around to compare to.

The Nightlight from Gossamer Gear gets high marks around here. My impression is the Z-rest comes in a close second for comfort.

I personally cannot get comfortable on them on most surfaces, though. Too bad for me!

I've tried from 2.5 inch inflatable BA insulated pads, to GG NigthLight egg crate pads, to 3/8" closed cell foam pads, to 1/4" GG ThinLight pads. What I have determined, at least for me (YMMV), is that site selection is what really matters. If I sleep on hard desert floor on a 2.5" inflatable pad, I won't sleep any better than on the 1/4" foam pad (which won't be very well). All the pad does for me is #1 insulate me from the cold ground and #2 make the sharp objects I'm sleeping on less uncomfortable.

So as the ultralight maniac I am, nothing is substantially better than the lightest option, so I go with the 1/4" foam pad for my 3 season gear. I simply chose to sleep on top of some type of natural padding/insulation, and I sleep great on my super thin pad.

"What's the most comfy foam pad of them all?"

The one you sleep on on your back.

Perhaps the Ridgerest Solar or Ridgerest

The Z-rest was about 33% more comfortable to me than the standard thickness ridgerest. The egg crate bumps went flat really fast though. So for comfort for more than a couple of weeks of use, I'd go with the Ridgerest Solar since it's 1/8" thicker than the non Solar.

I <3 my TAR Z Lite. Best CCF pad around. TAR RidgeRest close second.

I would have to suggest the Z-lite. If your pack can work with it's awkward shape and lack of "burrito"- ness then it's really the king (it's also yellow, which represents it's royalty, gold). I thought alternating your sleeping habits was kind of unreasonable but if you think about it I guess it's not. I guess just in general we shouldn't adapt to our gear.

Happy Hiking

Will the z-lite really flatten out after only a couple weeks use? Im a lighter guy- around 150. Seems like a waste if it does.

I don't see you having a problem. I used mine on my AT thru and it is noticeably flatter now, but I still find it comfortable. And it definitely took longer than a few weeks for me. It was a pretty slow process over a 5 month period. I started my hike around 165 lbs and ended it around 145 just to give you a frame of reference.