Mike wrote, "[G]iardia... is the main culprit of water borne illness.... Aqua-Mira drops are superior in their ease and versatility."
Drops have only a fraction (1/3) of the active ingredients of tablets. Drops are meant to treat ONLY bacteria. Read your AM liquids instructions.
Tablets (3x the concentration of drops) can treat protozoa (giardia, crypto, etc.) in addition to bacteria -- although treatment time can be long (up to 4 hours). Again, read the instructions.
Drops are less potent and less versatile -- and should be used in places where users are confident that their water sources are protozoa free (giardia included). Just how one can be sure out there in the wilds is beyond me.
Liquids - treats bacteria only - 20 minutes treatment time.
Solids -- same as above in treating bacteria. However, its higher potency makes it effective against viruses and protozoa as well. Treatment time for protozoa: 30 minutes for water at room temp -- longer for colder water -- up to 4 hours for water just above freezing.