I'm going to be going over what I think to be the best five siege defenders now. Before this list starts I want to first say that these five operators are based around high level ranked play and the competitive side of the game these five operators are not based on which ops are more fun to play but instead off of which would be the best pick for you and your team.
Smoke
Smoke has one of the best kits in the game with his primary shotgun to make rotate holes, open hatches, and make the line of sight holes. Alongside the shotgun, he's got the secondary SMG 11 which most would consider his primary. As for his secondary gadgets, he's got the choice between a deployable shield or barbed wire with as powerful as the shields are after their buff this is usually what I take.
Finally, his primary gadget the smoke grenades smoke has one of the best gadgets in the game without a doubt. He can play Smoke in so many different ways he's probably one of the most flexible siege defenders in siege right now.
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Maestro
Maestro is very strong right now and one of the first things you think of when you think of maestro is his primary SMG. This gun is one of the strongest if not the strongest gun any siege defenders have and one of the best guns in the whole game even after it's nerfing like of the ACOG being removed it's still very powerful.
So maestro also has a ton of utility with his shotgun pistol sidearm to shotgun open any rotate holes, hatches, or line of sight holes through the floor or the roof anything like that. Not to mention his impact grenades so that you can use them to impact your walls or hatches or even just make rotate holes. All of that alone makes Maestro one of the best defenders.
Jaeger
Jaeger is the best at clearing and destroying enemy throwables without a doubt whether it's an ash charge, frag grenades, flash grenades you name it Jaeger has got it. His very strong primary and reliable secondary pistol, Jaeger has some of the most powerful weapons on defense and he can really take out anybody he needs to on top of all that he also has a barbed wire or a bulletproof camera for some extra intel if that's what you find useful.
Mute
Mute has an awesome set of weapons just like Smoke does with the shotgun and SMG-11. He has a Nitro Cell which can also be used as plantain isle if someone's going for a plant you can Nitro Cell from below you could just chunk a Nitro Cell through a wall, anything like that denies that plant.
Finally, for that Walden, Mute can double as either wall denial or jam any attacking drones from entering the bomb site or wherever it is you want them to not drone. This makes mute one of the most flexible Rainbow six siege defenders.
Echo
Finally, our last siege defenders of the list. Echo is somewhat similar to maestro and you'll also often see either Echo or Maestro duo. So I feel as if it's going to cover both of them here. Echo has a great set of weapons with his primary gun which is actually stronger than doc and rook's mp5 which a lot of people actually don't know.
Alongside that he has his secondary bearing 9mm SMG which is great, it's why most people would run on him for his secondary gadgets. He has got the choice of a deployable shield or a barbed wire and again with the recent buff of the deployable shields.
I personally prefer the shield as for the primary gadget he's got two of his drones which are very useful for getting intel and denying plant later on the round. All these things put echo on our last spot in the list of top 5 best siege defenders.