When the Ford Escape first came out a car magazine (sadly, I can't remember which one) threw it into a comparo with several larger SUV's. IIRC, I believe there was a Tahoe, an Explorer, and a 4Runner involed. They got the Escape to go everywhere the other big utes went with little difficulty.
The Escape/Mariner uses a real 4WD system instead of AWD like many small utes are going to these days which helps it out alot off road. They'll get into the mid 20's in gas mileage, but I'd say they'd be worth a look if you want something smallish like the RAV4. For something a little larger I would recommend a 4Runner all the way (I'd look at an '01 or '02, but I prefer the older bodystyle). They're great off road and you can get low 20's on the highway.