"But normally you can't carry more FAK stuff in a PSK than some band-aids, alcohol swabs, antibiotic ointment and perhaps some tylenol.
Is the space that those items take in worth it? Or would you choose for extra survival supplies?"

I don't carry any band aids in my PSK. For band aids, I have a sterile towel and duct tape. I can cut them as necessary to make little band aids or big bandages. The towel has many other valuable survival purposes, from insulation as a scarf or hat, to 1st stage water filter, to tinder, etc. The duct tape has many other uses, too, from gear repair, to makeshift sunglasses, to binding material for shelter building, etc.

I don't carry alcohol swabs. I'd much rather clean a wound with diluted povidone iodine, because it does less tissue damage. The small squirt bottle of povidone iodine hardly takes up any space or room, and the iodine can be used for water sterilization, as well as for wound cleaning.

(By the way, I do usually carry a couple ounces of pure methanol, for my job, so I would likely have this on me, in an emergency. While it is not my preferred wound cleaner, it is commonly used for this purpose. It's also great for fire starting.)

See what I mean, that the items can serve both PSK and FAK functions?

I do carry some tablets of medicines in my PSK. I think these are very worth carrying. An aspirin not only relieves pain, it can also reduce swelling, and lower fever. Even aspirin has PSK use as well as FAK use, since it can thin the blood, and thereby slightly increase circulation in the extremities, helping to prevent frostbite.

So, to directly answer your questions: PSK space for survival supplies is at a premium, but I don't need to choose between first aid supplies and survival supplies, because they are the same supplies, generally speaking.