It is recommended that you get at least 400mcg of folate
daily when trying to conceive. There is not one brand of folate that is better than another. Also remember, you can folate from food that are fortified with it, such as orange juice. You can google "folate rich foods" and get a nice list.
Also, most generic over the counter "prenatal vitamins" contain 800mcg of folate. This would be adequate for anyone trying to get pregnant. From my experience, the only advantage of one pill over another is potentially the SIZE of the pill. Often prenatals are large pills, but some of the more expensive name brands are smaller.
I hope this helps! Good luck!