Of the three the Share would be my pick for two reasons. First, it will be the easiest to keep in because of the larger pony (although a harness still helps). The way they're set up the Feeldoe requires more strength to keep in because of the bulb design.
Even with a harness a double adds increased stimulation and a bit more control for the wearer. The Share cradles the vulva a bit, so when you thrust in and grind it stimulates the giver. The Feeldoe has a vibe, but it contacts less of the female genitalia during use.
Secondly, the Share is a softer toy, which means that it will be comfortable for the getter in more positions. I find the Feeldoes are a bit more "position sensitive" - in some positions they're comfortable, in others they poke too much.