I switched to the oil bath type wheel bearing lubicators about 3 years ago and have been super happy with them. No chance to over fill or over pressurize the seals, no accidental grease splatters all over your boat or trailer members, no grease gun reqired, easy to check fill level.
Wasn't sure about them when they came in the Kodiak disc brake kits I bought but now I am sold. There are two types though. One has a clear cap to allow you to view the oil level. The other has a solid collar (like a bearing buddy) with a rubber plug in the center where it is protected from accidentally getting hit or cracked. This is the preferred type even though you have to pull the plug to observe the oil level.
In my mind, they are a significant upgrade over grease.
