As far as safety the boat hook suggested has dual air chambers which can be good if you have some sort of an air leak or blow out... however it will still drop you in the water which could be near freezing and dangerous, but you can always prop your self up on the inflated side to keep the top of your waders out of the water and thus keep the cold water out of your warm waders and keep you warm while kicking back to shore, which could be a good distance away and even further from warmth.
Safety has more to do with
YOU than the boat. You should learn the dangers of the water and the cold and more important...cold water.
And a wading belt would be a good idea in a tube in case you go down, they won't drown you but will keep water out of your waders. Again more important with a cold environment.
I remember taking a dip in a kamloops lake in the middle of summer on a warm day, the clouds were over head and it was windy, I fell out of my boat doing something not so bright and even though I was back in my boat within 5 seconds I was soaked and the wind was chilling me off pretty quick...luckily it was summer and not cold out!
You do not want to be wet and in a cold environment! That is the real danger besides not wearing your pfd.
Most of the dangers I talked about involve the cold and in the warmer months are not a big issue, however some lakes are glacier fed and stay very, very cold year round not to mention they can be remote hike in and a good distance from your car(warmth).
And if you buy a used tube make sure to check it out, the inner tube I mean for damage, wear, or signs that could lead to problems before you head out. I'd probably even look at replacing the inner tube if it looked to be on the old side as a precaution. Kinda like changing the water pump in your car before it breaks. But it all depends on what you are doing with it I guess.
If I had a choice I'd go for the outcast boat hook recommenced hands down... well as far a float tubes go.