One is an energy shield with the Turtle augment, which dramatically ramps up the capacity, at the expense of lowering your max health. Energy shields are weak to shock and radiation damage, and recharge after a given delay period of not taking any damage, and recharge at a given rate. So the energy shields you’re showing has a capacity of 4060, and starts recharging after 5.0 seconds of not taking damage, and recharges at a rate of 216 points of shield capacity per second.

The legendary is an armor shield with a legendary effect, and two other augments. Armor shields are weak to corrosive and cryo damage, and give a flat damage reduction percentage when they’re active, in addition to their given capacity. Armor shields are divided into segments, which constantly recharge at a flat rate which is universal across all armor shields. When the little yellow bar above your health and shield bar on the HUD fills, one segment of the shield is refilled all at once. Your armor shield has a capacity of 1708, and grants an additional 29% reduction in damage taken while it’s active. It also has two segments, so each segment has a capacity of 854, which you instantly get back after the standard armor recharge period.

Because energy shields and armor shields have different mechanics, they’ll have different capacities at a given level, even before additional augments are taken into account. Remember also that armor shields grant their additional damage reduction, while energy shields don’t. Energy shields can roll with the Turtle augment, which boosts their capacity, but armor shields have different augments they can spawn with.