I hate grammar book...they always give these things as "pick which one you like coz they are the same!". Then you talk to some native speaker and they say they have a difference.
All these little "nuance" that you find here and there are so hard to understand for us foreigners. For example I have someone trying to explain me additional uses of は and I really don't see all those differences. I had finally reached the point to kinda understand the "nuance"of a phrase like 私に息子がいます and 私には息子がいます...but now I find out that I can even say 私は息子がいます...man I wish I could put in a Japanese man what Japanese learners feels like in these cases
