Can't tell at quick glance if either of those chargers are 3-stage type. Looks like you can only control amps to "high" or "low".
A typical 3-stage charger
will give you bulk, absorption, and float stages, and many will give you more charging
"profile" choices (separate voltage selection for bulk/absorption and float stages) so you can better match to what the batteries
If your previous Sears battery
was a Platinum Plus AGM, it was made by Odyssey and shouldn't have died in ~20 cycles. Could have been a lemon, but i'd first suspect that something on your boat
is the killer. The AGM-hood-ness (?) of the batteries
is likely not germane; same could have happened with wet batteries, too.