The mag type uses a strong magnet to affix the filter to the tank glass. I'd run it for a few weeks after you get actual fish stock in there. My experience with fishless cycling is limited. I think by the time someone learns the ins and outs of the nitrogen cycle they can successfully manipulate a fish in cycle safely by the use of cycled media, frequent testing, water changes, or plants, or a combination of the above.
Fishless cycling looks good on paper and makes for a great lesson in patience, but its just not something often seen among those with dozens of tanks.
If I fishless cycled each of the tanks I've set up since february I would have put at least 2 api master kit employees children through college.
Ugh I feel a writeup coming on.