I was dead set on a Grand Cherokee, but am so glad I went with the Tahoe (older version). I think that the tahoe with the 5.7 liter will get the same mpg's as the 4.7 Jeep, or pretty darn close( the new 5.3's are similar to the older 5.7's). Plus, the bigger engine and hopefully towing package will be beneficial also. The Jeeps aren't really known for being happy with a lot of weight behind them.
The size of the tahoe vs the jeep will probably make a bit of difference when towing. My old '97 does excellent - I could see upgrading to a newer one(tahoe or Sub) someday, but not going to the Jeep ever...unless it is for the second vehicle.
I believe most of the V8 Grands are full time 4wd, which really isn't useful towing.
The Jeeps are fun to drive, for just an "around the town" vehicle. Like I said, I was really close to pulling the trigger on a WJ. They will also pull your boat, but I'd go Tahoe. Also - 3rd row seating gets used all the time in mine.