Here are a few possibilities that come to mind, based on various aspects of planet evolution:
1. Akaria is simply in a non present Earth-like state while Obize is. For most of Earth's history the surface did not look like it does today. For instance, trees only came along in the last 10% of Earth's history (see here). Earth as we think of it -- with surface plants and ocean life and large animals -- did not exist for the first 90% of Earth's history. If you found Earth when it was only 3 billion years old it would not look like Earth.
For your story, it's totally plausible to imagine two settings in which one evolved a bit faster than the other. The reason why could be linked with the smaller size of Obize, e.g., becuase its interior cooled faster so there could have been more vigorous tectonics early on. Speculative but not crazy.
1b. On a more common vein, Akaria could be trapped in a "snowball Earth" state whereas Obize is not. It would be an icy desert instead of a hot one, but still not habitable. 208
(e.g., see here).
1. Akaria got stuck in a prolonged magma ocean phase while Obize did not. When rocky planets form, the heat that is involved in giant impacts creates a very hot (basically molten) surface. Planets farther from the sun cool off faster than close-in planets (see here). Large planets also cool slower than small ones. So, you could imagine that Obize escaped this phase early on and retained a large fraction of its water but Akaria had a long (~100 million years or longer) phase that led to complete planetary dehydration and a desert planet.
2. Akaria is actually a Neptune-like planet while Obize is a terrestrial planet. Statistical analyses of exoplanets of different sizes have found that the division between "super-Earths" (large rocky planets) and "mini-Neptunes" (scaled down versions of Neptune) is at about 1.5-2 times Earth's size (see here). So it's plausible that Obize is simply more like Earth and Akaria is more like Neptune. If you want to go that direction....
Interesting question. Those answers are what jumped to mind.... 188