I currently have 4 pins and a United puck bowler from '69. That's all I have room for (translation - that's all the room my wife says I have).
To each his own, but I like to have a bit of variety. I was recently thinking about moving one of the pins out and replacing it with a rifle game or pitch and bat.
When it comes to guest preferences, they like the pins but love the bowler. I think it just lends itself more to group fun.