To add to what Thomas said.Rubber seals are not a good idea for use in motors. 50degree c over ambient approaches the breakdown temp for many types of rubber. A seal made from high temp rubber is not as flexible so save your money and stay with the zz shields. Notice I used the word shield. Seal manufacturers will tell you there is no such thing as a "Seal". If there is running clearance there is room for water vapor and dirt. Any device when stopped and cooling off will suck in dirt and water vapor regardless of what you try to use to stop it.
Also... Most people pump grease into a bearing until the see it come out. That keeps the bearing guys in nice cars and new boats as that forces the "seal" open and allows bigger dirt to get in. READ the bearing catalogue and don't listen to the "experts".
A failed motor bearing is almost always a symptom of another problem that caused the bearing to fail.
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The 2RS are sealed for life bearings i.e. the grease within the bearing cannot get out or contaminants get into the bearing and damage it. The ZZ are just a metal shield to stop larger contaminants damaging the bearing. Other than that the bearings are identical, it all depends what environment you are using the bearings for.RegardsAndrew
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