All other things being equal, the Lexus should last longer. But that’s from beginning-of-life, which means the Lexus you’re looking at is already 5 years older, which means that even if it lasts 4 years longer than your Subaru, it will still die before the Subaru.
And that’s assuming all things are equal. 90,000 miles is a lot of time for the previous owner to neglect the car. The most reliable car in the world turns into a hunk of junk if the owner doesn’t maintain it.
If I were wanting to replace that Subaru, I’d be looking for a Lexus that was at least as young as the Subaru if not younger.