My thought ....
“Better” is subjective. Other than not having to water, and reduce corrosion in area of battery, what do AGM batteries provide for you? Flooded are cheaper and can be better value per Amp-hour if comparing similar quality.
On new installations/designs AGM offer more location options, but on an existing motorhome originally designed for flooded, I’m not sure AGM add as much value.
Also, did Costco batteries fail due to being “cheapo”, or possibly something else? How long did original last? The motorhome isn’t that old to have gone through two sets of batteries unless original batteries were damaged before delivery.
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