Recs.
Updated
SpecsUpdate
Pros
Pro Great variety of playable classes
You can choose from 10 characters on each side (total of 20) to find the ones that suit your preference, or to explore new, unfamiliar aspects of the gameplay.
As an example, there is Sledge who uses a hammer to break through walls, Flash who can blind the enemy with flash bombs, and Frost who can set up traps to neutralize enemies.
Having such a wide variety of classes not only adds depth to the gameplay, but also keeps it interesting for a long time.
Cons
Con Ranked play can be discouraging
Not only does Rainbow Six Siege have a very steep learning curve, requiring you to learn map layouts, classes, weapons, and various gadgets, it also has a pretty volatile and demanding community. Even though you can play in ranked matches when you reach level 20, you'll probably get your butt kicked and get promptly flamed by your teammates. This is mostly because of the expectation that you should know everything about the game before you play ranked matches, which is only around the level 60 mark. If you happen to make the mistake of trying them before then, it might leave you with a bad memory that prevents you from wanting to try ranked play again.