I got another H!Nowi...

So I just got another H!Nowi, my original has +spd -res, my new one has +res -HP should I merge for a boost to atk and HP or keep, if something comes up, or if any of you have any suggestions?

I am also going to follow up on a previous question I posted: now that I have a 4* tharja I will not think about excicuting my 5* +1.