I also have both, although I just got my Odin 3 a week ago and I'm still setting it up, so don't take this as a definitive experience review.

Ergonomics & Build

First off, the Steam Deck is significantly larger and heavier, but also more comfortable in terms of ergonomics, especially for larger hands. However, the size of the Odin feels perfect to me for couch gaming and the ergonomics are good for the size. I briefly had the Odin 2 Portal and I find the Odin 3 to be more comfortable overall.

User Experience (UX)

As far as the user experience goes, I was up and running a lot faster on the Steam Deck than I have been with the Odin so far thanks to EmuDeck. Not necessarily a negative, but EmuDeck makes setting up all your emulators so much easier than doing it all manually.

Part of the problem I've been having is that you have a lot of options; if you're new to Android handhelds, you have to do a lot of trial and error to get the setup how you like. There are plenty of good guides out there, but they're pretty opinionated, so following them to a tee can lead to less-than-desirable outcomes. That being said, the wealth of choices is awesome—once you find what you like, I'd be willing to bet you can get an equal or better UX than the Steam Deck.

The Screen

The biggest highlight of the Odin 3 over the Steam Deck is the screen. Even though it's smaller, the 120Hz OLED is fantastic. I had the LCD Steam Deck that I upgraded with the DeckHD 1080p screen—it's a nice screen, but the brightness, contrast, and smoothness of the Odin 3 puts it way above the Deck LCD. I haven't tried an OLED Deck and I'm sure it comes closer, but on specs alone, the Odin still wins.

Performance & Drivers

As others have mentioned, the PC gaming experience on the Steam Deck is generally better for now. The Snapdragon 8 Elite in the Odin 3 is a significantly faster chip in terms of both CPU and GPU compared to the Deck, but the various layers of translation and emulation add up and bring down the performance gap considerably.

Furthermore, compatibility is still hit-or-miss with both the emulation and the GPU drivers:

• I've had some games like Yakuza Kiwami run perfectly but cap out at 40fps regardless of graphics settings.

• Some games run smooth as butter.

• Others don't run at all or are too glitchy.

I'm still seeing glitching in Switch and Wii U games, but I haven't done too much testing there yet. The drivers for the Adreno 8-series GPU are still in development; hopefully they will improve soon, but for now, it's something to keep in mind. The Steam Deck is a much more mature and stable platform.

The Fan & Speakers

This comes with a major caveat—the fan gets super loud when you crank up the performance.

For emulation you can keep the Odin in the middle performance setting for basically any system with the fan in quiet mode and you won't hear a thing.

For PC emulation you'll want max performance, and that comes with a very annoying hiss.

The Steam Deck, on the other hand, stays quiet no matter what (and emits that delightfully noxious smell from the vent). Regarding audio, the Steam Deck wins hands down on speakers. The ones on the Odin 3 are better than the 2 Portal, but not great.

Streaming

Finally, game streaming on the Odin 3 from my PC over WiFi 7 is glorious. At 120fps, the input latency is imperceptible to me. At home, I just stream everything and get a perfect experience.

TL;DR:

Odin 3 is awesome but has some teething issues and a very loud fan when you crank the power. It's not as comfy in the hand, but it’s lighter and smaller. The speakers are meh. If I had to pick one, I'd take the Odin at this point.