Look at the two returns, side by side, line by line.  Also be sure you answered all the questions consistently between the two.

Yes, I did compare side by side and H&R Block refund is $400 more... Why?

Ok...where is the difference exactly?  What form & what line?

they are identical...

They cannot be ... both returns are really just long  math problems and if each had 2 + 3 then they both must equal 5.  Compare each line of the form 1040 against each other to find the difference.