We recently adopted a dog and have enrolled her in an obedience class. One thing the trainer told us is never use a retractable leash because you don't have control over the dog. She recommends using the standard 6' nylon leash.
You CAN have control of a dog with a retractable leash. My dogs know where the end of the leash is, they come when called when they are on it, and I can shorten it if I need to. But they have to be trained ON a retractable lead for it to work- if you train on a short leash, and then go to a retractable one, you may not have control.
Premier Pet makes a no-pull harness that I like better than the Halti or Gentle Leader, especially for short dogs. A lot of dogs hate the head collars, but they don't mind the anti-pull harness (called... hmm.. Easy Walk.)