Agree. I've learned an approach to picking up new things, solving problems, and thinking things through such that I get it right the first time more often. It's a measure twice cut once type approach. Where as, my younger self would just start trying things and would end up getting it right eventually. It felt fast but took longer and might have had some collateral damage depending on situation.

In what way are you slower then?

I'm 43 and probably slower in the sense that I'm slower at producing code.

I'm slower because I think more about the code I produce. I have a wider knowledge of the domain I work in, cross cutting concerns, and technical choices that I'm taking into account when producing code. So I arrive at a more-correct solution faster.

I would say the tradeoff is worth it, but of course I would because I'm not in my 20s. If faster while missing more security issues, performance problems, and corner cases is what you want, my 20 year old self is probably better.

Reflexes, movements, manual tasks, repetitive tasks

Because a big aspect of intelligence is compression and decompression. As people age they have more context already available so there is more to draw on (automatically) when solving problems or learning. So less distance to get there.

You probably aren't any slower. One difference that I think I've noticed between older and younger devs is that older ones tend to be slower to actually write code than younger ones are. But the code they write tends to be closer to correct, so less time is needed refining and debugging it.

So it can look slower up front, but over the span of the entire task, it's faster.