Differences between the two:
The Dead/Zombies
28 Days later:
Started as an experiment..'Rage' not really dead just enraged (like permanantly high - dangerous)
Infected by any fluid transfer (i.e. blood drop in the eye)
Drive: Kill all people just because
Method of killing: Head shots only because any other wounds wont really slow them down (ie like a crack addict they keep coming)
They can Die by starvation because they are still 'alive'. Theorically they could die as any human can, drowning, fire, etc.
Living Dead:
Unknown origin
The Dead are.. Dead. You must die first before being 'turned'
Infected by bite. Generally speaking those bit and turned are usually ones who think they can survive after being bit and hide themselve until they turn. Most living dead will stay on the scent of a 'live' one until it turns they they lose interest. Living dead will nealy completely eat a live person until they turn (ie. one living dead movie where the living dead only had upper torso.)
The Dead are Dead and they can not be killed by any other method than a head shot. They can not be drowned, they can not be hurt (ie. they lose an arm it's ok). They can be burned however, as long as it's the brain that's destroyed as well.
Because they can not die, you can not wait them out. They will find you. Until this latest movie, however, they were slower (zombie-like).
Question of Cross Continental Travel:
28 days later: UK only. The news well spread and immediately the island was quaranteed.
Living Dead: Due to the fact that you turn so quickly, it's nearly impossible to make it off continent. Only modes of transit are boat and air. Planes with dead can not land, hence they are destroyed along with the dead. Boats can float to land and spread the virus but generally that's just hit and miss. Theory is more living would know by then and make this impossible.
Whew.. now there's too much about a movie theory!!! LOL
Favorite Scenario: the freeze dried living dead. The army kept them to see if they could find a use for them (drop a few 'dead' on an enemy camp). Freeze dried you can see the living dead's face through a small window. Then an idiot private bumps the cannister and it 'rehydrates'. By the end of the movie all the 'dead' are burned.. people are safe.. but then it starts to rain and the 'infection' gets into the public water system.