As always some excellent points have been presented.
As for ruggedness, I don't do any offroad driving (well, not intentionally), so tearing up the vehicle wouldn't be a huge concern. I certainly concur that the Escape and the Highlander seem more suited to urban driving.
The maintenance needed for complicated hybrid system is a major concern, especially with the Escape, as it uses the braking system to help keep the battery charged. I'm not sure what the Highlander uses, I need to do more research. I would think that an extended warranty, very specific to the hybrid system, would be well worth considering.
I'm not sure about a Liberty diesel, the gas mileage for the diesel four cylinder seems to be less that what my in-laws get in their gas powered four cylinder Highlander. Also the more expensive diesal fuel seems to offset the gain in MPG, if indeed there is one.
The hybrid option in the Escape adds about $3,000.00 to the regular price. I'm not sure about the Highlander.