Natural = Y
Synthetic = N
I have used doe in heat and tinks during the rut and have found it effective. New problem is that some states are banning the use of natural lure, due to fear it could spread CWD. This has prompted the development and sale of synthetic deer lure. I'm not a wildlife biologist / scientist, but I'm convinced that they can't produce something as effective as the natural product. It seems they are trying to offset millions of years of evolution in an animal that has a sense of smell about ~10,000 times that of humans. According to whitetail101, the deer's long nose has 297 million olfactory receptors, humans about 5 million.
The less you can do to alert / tip a deer off, the better.
YMMV