This subject has been discussed many time in a lot of forums over the years.
There is no distinct advantage of one over the other. Except keep the dirt out , best as you can, replace when needed.
They have tested, leaving the shipping grease in the bearing, Ceramic bearing with super trick $8 per ounce oils.
(No oil at all, bearings did not last long). Lithium grease, regular bearing grease, used oil, new oil, slick 50, STP.
Not any measurable difference in actual racing conditions.
So pick any method that you like , just keep the bearing turning smoothly. replace as needed. Seals once you remove them , Carefully, Will last. But not the metal seal. You can buy the machined seals and they help.