Carbocation Stability
The fact that the methoxycyclohexane carbocation is resonance stabilized greatly increases its stability over the the trifluoromethylcyclohexane carbocation.

The same power of oxygen’s ability to donate electrons can be seen in its effects on benzene rings. Both $\ce{-OH}$ and $\ce{-OR}$ groups are strongly activating groups, while $\ce{-CF3}$ is a ring deactivating group, meaning it actually pulls electrons from the benzene ring. This further shows that the methoxycyclohexane carbocation is the most stable of the 4.