One more vote for the Scotties. Ihave had two sets now, so you know I liked the first one (I sold them with the first boat, and got new when I got my newest boat). I use two downriggers, and will fish two lines per ball when I have that many people with me. I didn't go for the long arm ones, because I thought they would be unnecessary. You do want to be thoughtful about whether you kicker can get to the cable, and a long arm may be helpful there.

One thing to think about - the long arm rigs have the potential to exert more force on your boat if they snag. This can be dangerous for small boats. If you're using a smaller boat, stay with the short arms.