Tom, here's my 2 cents on those controllers you listed. First off Difalcos are my favorite controllers. They're tough! I've seen problems with other controllers, especially if you accidentally hook up backwards. I've only seen one issue with a Difalco.
The Difalco DD268 is the Fanatic model. It features multiple small potentiometers, one for each of the "bands" the controller wiper makes contact with. This controller has almost infinite adjustability. The compromise with this adjustability is the need to manually adjust each potentiometer for your baseline control. Once you have your baseline set you can adjust just like the other controller models using the sensitivity "knob". It can be time consuming setting up your baseline, depending on how particular you are, and the baseline settings may be something you want to change depending on tracks or cars. With this controller a notebook for keeping notes regarding settings might be handy. I have one of these controllers you can look at and try if you'd like before making a decision and purchase.
The DD281 is the top of the line newest Genesis model. The Genesis models use an interchangeable transistor network instead of the individual potentiometers for the wiper bands for the baseline settings. The only downside to this versus the Fanatic is; to change your baseline control settings you need to change out the "network" for a different one. For our racing that would probably mean one network for 1/24, and one network for 1/32. With the Fanatic you would just change each of the 12 or 15 potentiometer settings. The DD281 also comes equipped with a traction control potentiometer and the Pro brake potentiometer. I like the traction control option, but I'm not sure the Pro brake potentiometer is really needed for the racing we do around here. The DD271 is the same controller without traction control. I also have a DD281. It is the controller of mine you've used before.
The DD270 gives you the Genesis controller without the traction control and Pro brake potentiometer (uses the economy pot.). I think one advantage of the Pro brake potentiometer is it is less likely to burn up if you hook up backwards. The DD280 is just the DD270 with traction control added.
The DD304 Stan mentions is basically the DD280 but primarily designed for 1/32 racing. It comes with a network for racing 1/32 cars whereas the 200 series Genesis controllers come with networks for 1/24 racing. I'm sure this controller would work for both 1/32 and 1/24 with a network change. My personal choice was to go with the 200 series controllers for 1/24 because I feel the components are more robust. Most 1/24 scale cars use a lot more current than the 1/32 cars which means more amperage through the circuit.
When in doubt just email Jim Difalco for his advice. He is great about responding to email questions and will be happy to build you the right controller to suit your needs!
