Welp, it cost Nintendo at least one sale. I was planning to get the OLED Switch just for shits and giggles, but now I'm getting the 512GB Steam Deck instead. =P
But yeah, in the end, it doesn't matter. There is no real competition here, we're talking about two ridiculously different devices. Plus, Valve doesn't even have the logistics to compete with Nintendo. They will be lucky if they can manage to produce a million units in the first year. There is really no point in comparing the two. So just don't do it.
My personal opinion: Both are great devices and if you're a passionate gamer and have the option, you should totally get both of them.
Official member of VGC's Nintendo family, approved by the one and only RolStoppable. I feel honored.