If using chlorine dioxide, Micropur tablets (one tablet per quart or liter) is a much better choice than Aqua Mira (AM). A few points to consider:
1. Solid Micropur has about 4 times the chlorine dioxide than liquid AM. (*) Micropur is allowed to state on its label that it can treat all three classes of baddies: viruses, bacteria, and the harder-to-kill protozoa cysts (e.g. cryptosporidium). Treatment time is 15 minutes for the first two, and 30 minutes for the third. HOWEVER, if water is near freezing, treating the third baddy can take up to 4 hours.
2. In contrast, liquid AM is less concentrated, and is NOT allowed to state anything about protozoa. If you read the AM label, all it says is 30 minutes treatment time to kill bacteria -- that's it. Now, both AM and Micropur use the same ingredients, just different concentration. You can achieve the same efficacy with AM by quadrupling the number of drops used -- but that's both expensive and tedious.
3. With Micropur, you just drop in a tablet per quart or liter, and wait 30 minutes. With AM, you have to carry two separate bottles of liquid, count the number of drops, mix the two liquids, wait 5 minutes for oxidation to occur -- then pour the mixture into your drinking bottle/bladder -- and only then does the 30 minute countdown begin.
If one has already purchased AM, then continue using it by all means, but if starting fresh or replenishing, I would recommend Micropur over AM.
Finally, BPL sells a liquid chlorine dioxide that eliminates mixing. However, once opened, it has a shelf life of just 6 months, and BPL recommends refrigerating the bottle in-between uses. If I remember correctly, both AM (unmixed) and Micropur tablets have a 5-year shelf life.
(*) - According to a recent post on backpacker.com forum -- written after the poster had talked with an McNett AM rep, comparing specifically between AM and Micropur.