Barron's vs the real test - math level 2

I’ve read that barron’s is so much harder, but to my surprise, I was more intimidated by an actual test from the collegeboard. I don’t understand how is barron’s harder than it.

Are there any (Realistic) resources I can practice with apart from the official test released? I’m getting 730-770 on Barron’s but I find the real test more difficult (haven’t taken it yet, but I glanced over it and had difficulties solving practice problems on the collegboard website)

http://www.amazon.com/Official-Subject-Tests-Mathematics-Levels/dp/0874477727/ref=sr_1_3?s=books&ie=UTF8&qid=1464489678&sr=1-3&keywords=sat+math+2