The Smartballs are bigger that I prefer but I'm a fan of duotone balls. The have little weights in them that give you a rumbling sensation when you move so they feel nice to wear.
Also, the cord will make it much easier to use if this is your first experience with vaginal balls.
You might also be interested in Lelo's Luna Beads.
They make them in 2 sizes and they come with interchangeable weights so you can customize them to your preference.
Good luck with whatever you choose! And if you have any questions feel free to ask