I've got Ultegra hubs on my touring/commuting wheels. They are a good choice for serviceable bearings. I've had mine 2 seasons and have overhauled them 3 times now. I repacked after each of 2 week-long off-road tours because I felt some minor grittiness, but it was mostly in the dust caps and not in the bearings themselves, as the sealing mechanism is pretty good. Still, if you plan to ride cross-country through all kinds of weather and not service your hubs mid-trip, then sealed bearings might be a better choice. I was impressed with a DT hub we disassembled at UBI. On the other hand, Ultegra hubs are easily serviced by any shop in the country, and replacement freehubs would not be hard to find.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72