Once you have mastered the basics of guitar, it is important to branch out a little and find out what else you can do. Strumming is where you are going to start because it is the simplest way to play your guitar and it can get you to make music pretty much instantly. Chords are a lot more diverse, though, and just strumming them will not allow you to fully express the various moods that people associate with them. If you pick and choose the notes from each chord that you are playing, it will give you a lot more control over the music that you are making.
Picking is thus the next step that you should take in your guitar practice routine. This is because of the fact that you can avoid notes that might clash with the mood of your music. For example, the major third has a very specific feel to it, one that will take your song in a happy direction. Avoiding it and going for the fifth instead would enable you to give a more neutral sound, and thus keep the mood of the song much more ambiguous. This is perfect for rock music where happy sounds are not usually considered to be the way to go.
The best thing about picking is that it allows you to move into the world of lead guitar as well. As you start to learn how to pick out certain notes, you will be able to do so along a scale instead of just sticking to chords and the like. The importance of picking can’t be overstated, and it is essential that you use a pick to get the job done because you will sound more powerful in the process.