This has repeatedly been discussed over at the IPMS/USA forums many times so why not here?
The traditional 1-2-3 system has been in use forever and is the one most standard model contests entrants are familiar with. You put your model on the table, the next guy does the same, last man standing takes first. Elegant in its simplicity.
Elegant, but flawed in several ways.
Getting a first may mean you have built a truly impressive and great model. It can also mean everyone built really bad models but yours was the least bad of the bunch. It can also mean no one else entered the category that day. The latter two of these are hardly ”first class” firsts. As someone who has been judging at various levels for nearly 30 years, I’ve seen this happen quite often.
This also leads to the situation where in one category, several excellent builds get noting while in the class next to it, a marginal, or downright lousy, build gets a first. This, too, is quite common.
Getting less than first may mean your model was a piece of garbage or it could have been superb, but for a microscopic flaw that was not present on the first place model. That flaw may have needed flashlights, mirrors and an OptiVisor to find. The “flaw” may not even BE a flaw, such as the panel line in the upper rear fuselage of a Bf-109. Someone not very familiar with the aircraft may assume that was an unfilled seam, especially if the one next to it has had that panel line filled.
Asking why your model placed less than first can be a fool’s errand. There is no set answer. It could range from, “your fingerprints in the paint foiled you,” or “well, the judges really couldn’t find anything really wrong with your work but the next guy had less wrong with his work.”
How to improve in 1-2-3? Build to the class that has little entered and hope no one else enters it next year.
While open judging, as developed by the Chicago club with input from no less than Shep Paine, may be more labor intensive, 1-2-3 can also take huge amounts of time when there are two or more close contenders for an award. That leads to the constant complaint that judges are nit picking. And, yes, they are. They have to when they are tasked with giving out one first, one second and one third in a class.
In open judging, your work is evaluated and you are rewarded accordingly. If you and three other guys enter flawless models in a class, you each get a gold. If no one enters a really good model in a class, there may be no awards.
Using the open system also eliminates the need for splits and huge numbers of micro classes such as is regularly seen in 1/48 aircraft.
Using this system, if you ask a judge how you can improve and move to the next level of award, you can be given specific answers.
Ultimately, in 1-2-3, you're being judged by how well the other guy built his model. In G-S-B, you're being judged in how well you built your model.
Now, good luck to the guys trying to run both systems, that’s going to be a lot or work for the judges. My club uses both as well, but aircraft and cars are done with traditional judging and everything else is done with the open system.