OK, a question that really needs to be asked here:
- Are you looking for a plug to wear during sex or play, or a plug to wear longer-term like during the day??
This will help determine what will be more suitable for you.
As far as shape goes, the three you have chosen all seem good for both play and long-term, but the neck on the metal one is a bit short - you might find it less comfortable for longer wear because of this.
They all have a wide bulb and long thin neck, suitable for longer wear. Though you would also need to bear in mind the feeling of the base - the metal one has a really chunky base, so it might not be so good for longer wear.