Jim: While I mostly use mine without the tails, as I live in a subarctic semi-desert, we have had a bunch of Pacific Lows sweep through, and lots of deep new snow, about 60cm in total depth, in the last week or so, so I have bolted on the 8inch tails for the past couple of days.
The flotation is good, I don't notice the extra weight when wearing them, I do notice the weight of the tails when I strap them to my pack for the road-walk in.
There are conditions, like post-holing up or down slopes in deep, soft snow, where maybe the tails would be better left off--but you can do that easily.
The added length can be a bit disconcerting if strapped (lazily!) under the lid of your pack---with tails they are wide enough to snag door-frames on!