Just curious. I'm narrowing between that and Catholicism.

You mean besides the fact that, like all Protestant sects, it's an arbitrary, made-up religion completely unmoored from historical Christian belief and practice ?

Lutheranism is the sect that has caused the most damage in Europe throughout the ages, affecting everything from theological doctrine to philosophy to economy to commerce to popular culture, etc. This is, in part, because it synthesized and further transmogrified the errors of the heresiarchs of previous ages (i. e., Pelagianism, nominalism, etc.). It was, in a real sense, an prototype of modernism.

One of the greatest flaw of Lutheranism is how it has debased the notion of grace, one of the most important and impacting questions of theological discourse.

Rev. Father Garrigou-Lagrange in his work Three Ways of the Spiritual Life [Les trois conversions et les trois voies],  (Westminster, MD: Newman Press, 1950), shows how the Lutheran heretics have degraded the notion of grace and what is the true nature of supernatural grace according to the teaching of the Church.

Take special note of the footnotes on pp. 5-6.

I mean like, dogmatically and scripturally?

I will try to get a post out for you tonight.  Hopefully it will satisfy you and end your questions about why you should devote your life completely to Our Lord by living within His Church (that is to say, His Mystical Body).  It will be rigorous and thorough, since, I have to warn you, the answer to your question will be really long, since there is just so much wrong with the Lutherans dogmatically and scripturally and in almost every other way.  

It's kind of like this conversation :

"Do you have a favourite poem ?"
"Yes, the Iliad."
"Could you please recite it ?"

Not to fear, your answer is already being hatched as I write this.