It's dumb.

You're welcome to have opinions about your favorite series.  Personally, mine is Harry Potter, because it deeply affected my emotions and childhood.  However, fighting about which is better is just stupid and futile.  You can't change someone's opinion by simply arguing with them.

That said, I enjoy reading Harry Potter more not because of the quality of prose, but because of the universe, the characters, and the themes.

Some can argue that the Lord of the Ring's universe is deeper.  It isn't depth I'm looking for (even though JK is delivering plenty with Pottermore), the universe is just so enticing.  I don't enjoy saying so, but HP magic is better than LOTR.  The HP universe is set in real life, just in a pocket of it.  It seems so tangible.  And you want to live in it.  If you did live in it, life would not be hard.  The LOTR universe is medieval, harsh, and daunting.

The characters are amazing.  Every single one is characterized brilliantly over the span of 7 books.  There are a rare few static characters.  All change and grow through the books, which was a great experience if you read them as they came out.  You grew up with the characters.

The themes of LOTR and HP can be claimed to be very similar.  They both exhibit themes of loyalty, bravery, and the triumph of good over evil.  Throughout LOTR, these themes are exacerbated by darkness, danger, and suffering.  There are a rare few happy meals with elves, dwarves, or Rohan men until the very end, when all the characters exchange a tearful goodbye with Frodo.  Oh, don't forget the fact that the Shire, the Hobbits' home, was burned to the ground.  Happy.  HP balances these themes using light and dark elements.  At the end there is an upbeat feeling, the characters were wounded by the deaths of friends and family, but there were kernels of hope for the future.  At the end of LOTR, everything felt weary and near-death.

Regarding movies, I'm afraid there's no comparison.  Lord of the Rings is a clear victor.  The experience of the Harry Potter movies was probably better.  I've heard/watched so many beautiful stories of friendships formed over 10 years of filming together.  However, the HP movie series is marred by frequent director changes, rewrites, and lack of following the books accurately.  The Lord of the Rings had a very solid cast and crew with brilliant director Peter Jackson at the forefront.

I love both series.  They're both great book and movie series, each holding a special place in my heart.  I think it's stupid to fight and to try and change each others' opinions and to hold these opinions personally against each other.