Well, at least the base model Xbox Ally has essentially the same SoC as the Steam Deck. The Z2 A has 4 Zen 2 cores and 8 RDNA 2 CUs. It will be configurable up to 20 watts TDP instead of 15 on the Deck, but that’s it. So much for “long in the tooth technology wise”.
Sure, the Z2 Extreme variant will be more powerful, but it’ll also be in a different price category (800-900,-€).
And in terms of user-friendliness: the Xbox Ally will run Windows. It won’t launch into the regular desktop shell (by default), and it won’t have as many services running in the background which might help with performance and battery life, and you’ll probably be able to update drivers and Windows through it. Maybe it will have some preconfigured scripts/shortcuts to install Steam, Battle.net etc. But that’s it. Expect to fall back to the desktop mode (or open a browser, terminal and Explorer window in the new gaming mode) for anything more advanced like installing emulators.
In terms of pick up and play this won’t be much different to the Steam Deck, with the one exception being Game Pass - but even then don’t expect any of the more demanding titles to run well.
The ROG Ally X’s MSRP is 899,-€ and that’s what it currently costs here in Germany at least. It was as low as 799,-€ though recently, but now it’s back up. Considering this “Xbox Ally X” is the successor to it, I don’t think it’s unrealistic.