Not exactly.
In many match ups they will perform identically, but there is a strong likelihood that in some match ups the higher att will ensure more damage.
Whether 1 att IV makes a difference is dependent on the individual opponent.
HP is just a fixed number determined by an algorithm utilising the stats. In some cases, rounding results in the algorithm generating the exact same number of HP for an IV stat of 14 as it does for 15.
