What benefit does a 737 obtain from higher thrust engines. Is it greater speed? Is it greater payload?
Any aircraft, if given more thrust, will have better take off and climb performance. It will be able to climb to higher levels earlier in a flight (note, not higher levels, just the same high levels earlier). As some of the weight limitations are defined by climb gradients, then those weights may increase, but it won't necessarily increase the max weights unless engineered to do so. You'll also have much better go around performance, and it may (but not necessarily) improve engine out performance. At the same time, it may make Vmcg/mcg higher (V minimum control speeds).
These particular engines combine more thrust with much better fuel burn, so combine that with the ability to get higher earlier, and you should dramatically reduce your fuel consumption.
Do the engine manufacturers get more money by selling higher thrust?
If you are leasing your engines (as more and more do) then use of higher thrust will cost more, so it's a trade off of the cost versus the saving. If you buy, then it will cost more, and your engines almost certainly will have higher maintenance and life cycle costs. Just like a high performance car versus it's slower siblings. The makes aren't blindly making engines with more thrust to sell for more dollars though. Getting a thrust gain whilst increasing fuel economy is an immensely expensive enterprise, involving some amazing technologies. The aircraft makers come up with a design, and then get the engine people to make them an engine for the job.
From what I am reading the 737 MAX is over engined for the design of its airframe/wings and rather than embarking on an extensive re design Boeing chose to fit compensating software.
Not really, in the sense of too much thrust. The issue with the 737 is that when it was designed by stone age man, he decided to have it sit very low to the ground, and stuck two very thin turbo jets under the wings. Over the years engine design moved on, and they are now much fatter, meaning that they just don't fit into the space between the wing and the ground. So, to mount the engines away, they need to move them up, but there simply isn't room before you run into the wing. So, the solution is to move them forward, which has the effect of moving the thrust and drag couple. It also has the effect of creating a lift component on the nacelle, which is what is causing the issues at high alpha. This is well beyond redesign, you need a totally new aircraft. The engines are a squeeze on the A321NEO, and the 320 family has always had much better engine clearance.
Just like in a modern motor car software relies on sensors and I believe that a failure in this area may have caused the two tragic crashes of an aircraft which has proven to be almost indestructible.
Believe is a terrible word in relation to aircraft accidents. There's theories, and proof, but not belief.
Aircraft will always rely on sensors, and as they move towards a totally FBW world, they will do so more, not less. The issue here is not enough sensors, and software that was so poorly written that it relied on a single sensor, and was not smart enough to be able to differentiate between good and bad data. Of course, that is only true if we're seeing something related to MCAS again...so it's only a theory.
