The wheel was designed only to make sense for up to a couple of steps (Optimal-->Adequate-->Terrible)--and then only if you strech your imagination.
I've never been a fan of the wheel as it is anyway, though figured there was no point in whining since it was deciding at the dawn of time.
In particular though, why is Swamp right next to Ocean, why is Radiated right next to Inferno and why is Tundra next to Desert?
The problem is that the available selection of environments doesn't really work in wheel form... To avoid oddities, it should "really" be something like:
Swamp - Toxic - Inferno
Ocean - Terran - Desert - Radiated
\ \ /
Tundra - Barren
Which avoids things like hotter-colder changing in different directions depending on which side of the wheel you're on, which leads to the inconsistencies drek pointed out above.
That said, the whole "Environment Preference Wheel" concept somewhat depends on there being a "wheel"... so it'll have to do, I guess.
THAT said, there are a few omissions from the EP wheel / system, IMO...
In particular, there could/should be environments to represent planets like Saturn's moon Titan, which has a dense nitrogen-methane atmosphere (unlike the breathable atmosphere of tundra), but is colder than tundra (but not as cold as barren). Could go between tundra and barren perhaps... No idea what to call it though.
I'm not sure if inferno would apply to a rocky planet that's still molten (newly formed and not yet had time to cool and solidify), or if inferno implies a hotter version of toxic (hot and chemically toxic) Presumably the atmosphere of a molten rock planet wouldn't be particularily nice, but I'm not sure if it'd be up to "toxic" standards or not...
To deal with this and the (IMO) oddness of having inferno (hot, molten, chemically toxic) next to radiated (cold, solid, radiation covered), inferno could become explicitly radioative, and toxic could be described as a bit hotter, and radiated explicitly "warm":
Toxic: Tremendous crushing atmospheric pressure, corrosive acidic rains, hot enough to melt some rock and metal.
Inferno: Covered in volcanoes and lava flows, corrosive acidic rains, moderately radioative surface
Radiated: Thin to Earth-pressure atmosphere, rocky barren surface, bathed in high intensity radiation from within or externally, warmed by radioactive decay or heavy solar radiation
I'd also like it if there was a distinction between gas giants (eg. jupiter, saturn) and ice giants (neptune, uranus), which really are quite different in composition and size.
And something should be done about swamp being next to ocean... It doesn't make much sense to me, though I'm not sure what can be done...