Suction is one of the simplest suspension options for prosthetics. For general durability, suction is hard to beat, but the outer sleeve adds weight, and restricts movement due to the extra material. The sleeves also have to be replaced regularly because they'll eventually wear out and get a tiny hole, and even a pin-size hle means they won't be able to maintain suction which results in a pistoning effect with your socket and residual limb.
While most prosthetic supplies like liners can be replaced via insurance every 6 months, sleeves are generally eligible to be replaced whenever they're needed. Adding a gaiter or inner sleeve to go betwen the socket and outer sleeve can help reduce friction and extend the life of your sleeves, but at some point they will still wear out. In a pinch, duct tape can be a short-term solution to fix a small hole, but it will quickly wear out. For me, that's meant needing to bring more spare parts on trips when I relied on suction. If a sleeve got a hole in it mid-trip, I'd be in a tough spot without a backup, and since they're thick rubber, they definitely add extra weight when packing.
In my experience, one of the biggest benefits of suction systems is the overal fit and security. As long as there isn't a hole in your sleeve, they stay on snugly. However, due to rolling the sleeve up and down, suction systems are the most difficult to quickly take on and off. It's not horrible, but it's definitely not as simple as with a pin system.
For what it's worth, I've started using a sleeve with my hybrid pin/vacuum system so my leg is currently taking advantage of all three types of suspension. While most of my old sleeves have holes in them, the vacuum system helps ensure that's not a significant problem like it would be with pure suction. Using all three types means more time to take it on and off, but it's the most secure system I've ever used by far.
Editing by Kap:
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