The senior title is a rite of passage at Microsoft. Many stay at this level for years. It's less about the title and more about how you got here. It usually means, you've become a go-to person that has wide ownership. Junior teammates also come to you for mentor ship.
The only downside to this is that it's quite tough to go higher (the Principle level). Leveling up is always competitive but at junior levels, there are lower hanging fruit. The senior to principle move is like playing in the Big Leagues. The biggest reason why it that you're now responsible to determine "what the team should do." You'll have to be the one to hunt for great opportunities instead of being lead to ones when you were junior.