Having the Restube with you as a buoyancy aid may make sense if it is too hot for a waistcoat or if you are an athlete competing and need a very high degree of freedom of movement. It is also a great tool for swimmers to be able to trigger a buoyancy aid in case of a cramp, for example. However, the fact remains that this aid has to be triggered before it works, and that is a disadvantage in our opinion.
We share the view that with SUP paddling, you already have a perfect buoyancy aid with you in the form of the board itself: The board floats without being triggered ;-) You just have to make sure that it doesn't move away in case of a fall. For this, as already explained, the leash is as much a part of the basic equipment as the paddle.
We know from discussions: Restubes fans argue that the board could burst or the leash could break off under tension and in this case you would need the solution that is attached to the body. This view should not be withheld here, because this scenario also has its justification.
However, we are not aware of any case where an inflatable SUP board has burst on the water. Inflatables can burst if they are stored in the sun and experience a high increase in pressure due to heat, which does not happen on the water. Anyone who paddles a hardboard is out of this issue anyway ...
Our conclusion: The life jacket is the safer equipment compared to the restube.