Transportation engineer to the rescue! The weight of the trains would be transferred to the guideway through the magnetic field (like what happens when you try to put the "wrong" ends of 2 magnets together). The vibration and movement of the trains would be factored in with a "live load", which would probably be less with maglev than traditional rail, but not insignificant. As has already been mentioned, the trains themselves would likely be lighter than traditional ones, but the magnetic equipment embedded in the track would certainly make up for the difference.
While a maglev system would need to be completely separate from street traffic, it could run at ground level where it doesn't need to cross over/under streets. Depending what corridor they choose, this could help save some money in comparison to a tall structure for the entire length. If it's along an urban corridor, it will pretty much need to be aerial or below grade the entire time
One weight advantage for a fixed-guideway system (maglev, airport tram, etc) or light rail, when compared to traditional subway or Amtrak-type trains, is that the trains themselves can be fairly light duty. Since they won't be operating on the same tracks with freight trains, any impacts from a potential collision (with another passenger train or automobile) would be smaller, leading to a lighter design; from the sound of the article, any of the options on the table right now would have this benefit
Light rail would most likely be less expensive, but that's a pretty long trip for a light rail system. Generally speaking, LRT works best when stations are roughly 0.75mi apart (closer stations are better for buses, farther stations are better for subway-type trains); with all of those stops (and surface street traffic to contend with), the ~25mi journey from MCO to WDW would be quite slow and tedious
