The folks at MSR took their time getting this stove to market because they wanted to nail it. I think they did.
MSR played with heat exchangers early on. These were golden-vaned rings that slipped around the pan and re-directed some of the heat from the stove up along the side of the pan, making the whole thing more efficient, therefore requiring less fuel. That is important on a long winter trip, as often you have to melt snow to get your water.
The Reactor took it one step further and built a highly efficient heat exchanger into the bottom of the pot that comes as part of a system. The heat exchanger sits directly over the "reactor": it has no open flame, but rather uses a primary air combustion burner that allows the exchanger to sit right on top of the burner assembly. All the radiant heat as well as convection from the hot gases passing through the vanes on the heat exchanger.
There are two pots that fit on a Reactor base, a one liter pot and a 2.5 liter pot. For the test I used the one liter.
So, Mr. Science, what does that all mean? It means that the Reactor has the fastest boil time in the bunch. It is super efficient, and when backpacking or on an extended trip, you carry less fuel.
The official numbers state that the Reactor will burn for 80 minutes on one canister and will boil a pint of water in 1:30. I had a slightly different number for time to boil, but I have no reason to distrust the 80 minutes number.
Since the Reactor technology was introduced, MSR has created the Windburner, a modular Jetboil-like stove where everything is fastened together rather than having the pot sit loose on the stove. I've heard good things.
Downside? It's the most expensive stove in the group, and it only works with the pans designed for it, if you can live with that. Most folks can.
Decibels: 43 decibels
Fuel: Isobutane canister
Time to Boil: 1:40
Oatmeal Index: Use the instant stuff
Fueled by twigs, grasses, and driftwood, the Kelly Kettle made something out of nothing.
It slides together easily, and the workmanship is excellent.
One of the best stoves out there for frosty temps.
They last forever with proper care.
The Windpro is a go-to for backcountry chefs because because of its exceptional flame control and pot stability.
Simplicity and extremely effective, this is a very nice stove and an exceptional value.
Indestructible: if I dropped it off a 50-foot cliff, the Svea would light right up.