[Stop It]

Yikes, they should be covered for the same amount of time really all things considered.

The rated power is a bit of a red herring. A car battery is used as a starter device, so the Amp Hour rating isn't not as relevant as the Cold Cranking Amps. The CCA of Optima batteries are very high, and they generally last longer than standard Lead Acid batteries. The Amp Hour rating is more relevant for stuff like Caravan batteries, which is where Optima Yellow batteries come into play.

However, that Silver was very cheap, so I would've went for that too all things considered. As you say, sometimes the Optima's just wont fit anyway. Usually not a problem in my work's field however.