it really depends on when you'll be using the lights... I use mine on backroads a lot, so I use some ebay-specials that have a driving light-style beam. a definate pattern visible at 100 feet, although at that range it's around 10 feet wide per light. they're slimlite-style, so they have a pretty nice flood pattern, too. they brighten up around the XJ on the trails, but not annoyingly bright.
If you're doing mostly low-speed offroading, then just go with fogs. They'll throw the light around a lot more, and still throw it far enough to be useful as flood lights. If you're doing high-speed stuff (roads, desert), go with driving lights. If you have room for more than 2 lights, add long-range lights.
like I said, I'm running driving lights. 4 of them on my roof, two aimed around 100 feet straight out, and two arimed at the ground around 40 feet out. Two different switches, so I can pick which lights I need. the short ones are mainly for when the turns get scary at night, or some dipstick decides to cut out in front of me and drive 15 under the speed limit.