Question:
I don't mean which brand name, but which generic type. Over in the website misc.industries.utilities.electric (think that's the right name, I just type "rn utilities.el" in RN in my Netcom UNIX shell account) there's a thread arguing over the merits of ionization vs photoelectric smoke detectors. I would presume any detector approved by underwriter's labs (UL) should be better than having no alarm, and an alarm powered by the house's electricity is better than battery operated ones (no dead batteries).

Answer: Ideally, you would choose a detector that runs on household electricity with a battery back up. They also now have detectors that all wire together, so if you are upstairs in the bedroom asleep and the detector downstairs in the kitchen activates, it activates ALL detectors in the house, but only the tripped detector flashes... a more expensive system but well worth it considering what yo uare protecting...