Legion Go does not offer a cheap entry point for people who want to get started. Sure the hardware is strong and probably worth the price. But it does not change the fact that the cheapest Steam Deck model is still cheap to get, especially with the refurbished program with official support from Valve in mind as well. But for enthusiasts who want powerful hardware, the Legion Go is probably better.
My biggest problem with the Legion Go would be probably that its using Windows and not Linux, so this is a downside to me. The detachable controllers are nice to have and while I would not need them, having them easily replaceable is a big bonus to me. It's a little bit bigger than the Steam Deck and the Deck is already a chunky boi. When my research is correct, then the Legion Go is 200 grams heavier than the Deck? That is substantial.
and a slightly better battery life will probably be appealing to some
I want to see benchmarks or tests with real games for that. We had claims with previous handhelds too, where they promised longer battery life. But the reality was they did not last as long as promised or under very specific circumstances only. It has higher resolution and hertz, so it will need more power. And it's probably not optimized for low power settings like the Steam Deck with limited power settings does, but I am open to this.
there may be a bit of danger for Gabe Newell and his team
Not really. Valve (and Gaben) want this to happen. They want the handheld PC market to flourish, because they are pushing Steam and PC gaming forward and make it usable for non PC enthusiasts as well. Even if Valve stops selling Steam Decks, Gabe Newell and his team would not be in danger. Unless this was a sarcastic note; in which case ignore this paragraph.