Out of the four you listed, I have only used the Bendybeads. However, looking at the other three, they don't seem to be of the same quality and, certainly, some are made of less hygienic materials. Bendybeads have a very unique shape and offer quite a nice increase in size from top bead to bottom. They're quite firm, but require some guidance during insertion due to the shaft flopping around a bit. The handle is extremely useful, too.
I might be a bit biased because it is the only product of the four that I've used, but I can guarantee that they are a quality product.
Second place would be the L'amour Beaded Probe, third, the Rhapsodia, and in last place would be the Power Balls; they may be big, but they offer no graduation in size, and they cannot be sterilized properly.
Good luck, and I hope you enjoy whichever choice you make!