Frosted. Coated lamps (such as "standard" frost and soft white) are usually coated by adding silica dust to the inside of the lamp during manufacturing. Silica is basically just more glass so basically harmless. Much safer and more environmentally-friendly. Still, I miss true inside frost!
The "true frost" absorbs quite some light, so reduces the efficacy.
The etching method is a kind of compromise - way less significant efficacy loss, at the cost of not so perfect diffusion (mainly when lamps in direct sight).
And the silica dust makes more problem with contamination: Because of the larger surface, more gasses adhere to it, so it becomes a bit more complex to outgas the final lamp (that was the reason, why many makers did not offered that - they either did not master that process that well, or evaluated it as too expensive step).
