For me I like performance, so currently my choice is always iridium (NGK, Champion or Denso).
I have tried others, result is not good, eg. Autolite (too hot that cause pinging) or Bosch (too big gap for standard ignition).
The key thing is to match your ignition system, timing and the gap, this will make a big difference except for Denso with 0.4 mm tip.
When you use high power ignition system be careful when you use plug with small tip, because it may overheat and cause knocking or the plug lasts very short. Some NGK Iridium IX model also have platinum tip, that will last 100k.
If buy new car, you might be lucky if the car comes with Denso SIP plug, that is the ultimate plug in the market, however they do not sell the model that fit other car to the public yet.
It is too bad limited option for plug available is just because the patents that make manufacturer do not earn enough and do not want to manufacture it.