My personal opinion is, that I will only run oil bath bearings on my coach. Oil bath bearings lubricate better with less maintenance required. The only downside to oil bath bearings, that I have seen, is that you have to be diligent about checking for seal leakage because a leaking seal can cause low oil level and bearing failure. However, the seals that we have in heavy truck axles (diesel motorhomes) today, have a very low failure rate, and 100,000 miles on a seal without failure is very common. My coach has 110,000 miles on it now and I am going to change the original front hub oil and seals next winter in my annual maintenance.
Gerald