Very very briefly, the Force 5 was the result of AMF/Alcort's effort to design a 'sportier' one-person dinghy, compared to the Sunfish. Unfortunately for AMF/Alcort, the Laser was introduced just around that time and won the battle for that market. In some ways, this was too bad, because the Force 5 had some advantages over the Laser. But that is history.
By now, almost 200,000 Lasers have been sold, and very few Force fives. But if you get your hands on a decent Force 5, have fun. As with the Laser, the optimum weight to sail the boat in breezier conditions is around 180 lbs.
I own both a Sunfish and a Force 5. I love the Force 5 for taking people out sailing. There is more room than on the Sunfish and the boom is naturally higher and easier to get under. It is great for taking little kids out for a sail.
I picked up a used one (Alcort '74) a few years ago for $500.00. With a little TLC and a new sail I ended up with a pretty decent boat.
I also raced it a little last year. I found the Force 5 group to be very friendly and helpful. They have a nice format for their NA's. It is usually a Thursday, Friday, Saturday event with an optional practice race on Wednesday.