which is more cancer-dangerous?

my mother was sugested these two options.
is there statistics on this?

This question doesn't have a simple answer. What we do know is that Premarin (congugated equine estrogens) has been shown in studies to increase risk of breast cancer, stroke, and heart attacks/heart disease.
Some studies show that bioidentical estrogens have much less risk of the above, but realize these studies are not as broad as the Premarin studies.
Estradiol (like Estrace) does not appear to have the same level of risk as Premarin.
Aeron's website ( I think it is Aeron.com) has good information on bioidentical hormones.
Each woman should fully discuss her unique risks and benefits with her doctor. If your doctor isn't comfortable with discussing all the options, find one who is.