I made this exact mistake when the Switch OLED came out. I got caught up in hype, I bought the new one, and slowly it dawned on me that I just spent 300 extra dollars for exactly the same machine I already had, and a screen that, as good as it was, was NOT worth that 300 dollars.
If you don’t own a Steam deck, then go nuts! Do what you want.
If you already own a Steam Deck, you already own everything you actually wanted a Steam deck for. An OLED screen is not going to make the games you already play somehow magically better. You’re fine. Chill out
The Deck v. Switch argument here doesn’t quite match though. OLED performance is higher with a 90Hz refresh, better potential FPS due to the faster memory, longer battery life, etc.
That said, if you do already have a Deck, you’d be better served to just learn how to take it apart, and get a 1TB 2230 SSD from OWC for like, $70. Boom, now you don’t need an OLED Deck because you can just have more games to play now.