Yeah, all electrical devices do require a backup of some sort of backup if you will be placing your health at risk with them. Map&compass for GPS, chemical treatments for steripens. Campfires for cooking, etc. Not to say that MuV, Steripen, MIOX, etc are not all good products. All will do the job. With plenty of water sources around, they likely represent the lightest/quickest water available.
The Adventuror (I have used the MuV, and MIOX, too) is my choice for light weight trips. The Sawyer does not catch bacteria from unknown sources, small and viable gardia, viruses, etc. The Steripen doesn't catch tape worm eggs.I have said before that staistics and tests are no guarentee of safety. You may get Crypto even double filtering with too large a filter, or, double dosing with UV, or, following directions with iodine, or, with improper handling using AquaMira. $hit happens. (Oh m'god, a pun...)
Most waters in the north country(at least smaller free flowing streams, ie those without dams) are likely OK. So, I carry no backup for the Steripen through most of my regular hiking areas. For new areas (at least new to me) I do. Spare batteries and a pair of half full mini-droppers only adds 2oz (though a purist may complain about the extra weight.) Instead of my usual liter of water (well, actually 1.2L in 2 gatoraid bottles) I bring one, if I am crossing a lot of water sources. Generally this weighs about a pound. So, I am saving about 8oz overall. Fiddle factor and wait time is virtually eliminated.