3 speed transmission bearings

[roadster36]

I am starting the rebuild on some transmissions if have and noticed that there are several choices for transmission bearings available. The vendor has listed bearings that are open on both sides (stock), bearings open on one side only, and bearings that are totally sealed and closed on both sides. The vendor states that closed bearings cut down on rear transmission leaks. Has anyone used these ? I know that most of the r leaks I have had over the years were from the countershaft not the bearings. Thank you - Dennis