Which is better for walking the dog at night?

The G55 gives more light and reach for spotting hazards, but its high mode lasts only 1.5 hours. The G32 on low runs 17 hours and is enough for a lit path.

Which lasts longer on a set of batteries?

The G32 on low, at 17 hours from two AA cells, against 21 hours on low for the G55 but from four AAA cells. On high the G32 runs 4.5 hours versus 1.5 for the G55.

Is the G55 worth stepping up to?

Yes if brightness and beam distance matter more than runtime. It is brighter, reaches farther, adds a medium mode and is shorter. If you want hours of light from AA cells, stay with the G32.

Do either come with a rechargeable battery?

No. Both run on disposable cells out of the box and accept Coast's optional rechargeable packs, the ZX555 for the G32 and the ZX865 for the G55.

Are they equally tough?

Both are IP54 water- and dust-resistant. Coast lists 1 m drop protection for the G32; the G55 shares the same sealed twist-focus design but is the lighter build.

Coast G32 Flashlight vs Coast G55 Flashlight

Both are Coast twist-focus lights with the same IP54 rating and PURE BEAM optic, so the choice comes down to output versus runtime. The G55 is the brighter, shorter light: 750 lumens and a 201 m beam, but only 1.5 hours on high from four AAA cells. The G32 is the endurance pick: 465 lumens, 134 m, and 17 hours on low from two AA cells. Owners of this Coast line praise the flood-to-spot twist and the pocket clip; the common complaint is that high mode drains small cells fast and that the rechargeable packs are sold separately.

Choose the G32 if you want long runtime on common AA batteries and a light that stays useful for hours on low.
Choose the G55 if you need maximum brightness and reach in a shorter body and will accept short high-mode runtime.

Prices

Coast G32 Flashlight: $18.97 at Academy Sports + Outdoors (checked today)
Coast G55 Flashlight: $29.15 at Surry General Store (checked today)
Difference: the Coast G32 Flashlight is $10.18 cheaper than the Coast G55 Flashlight today