MultiBit is a 'lite' client which downloads most recent block info, but is equally good & secure for most users.
Incorrect, Multibit is a SPV client which downloads the header of every block. SPV clients trust miners to enforce the network rules, full-chain client does not trust miner this way. Bitcoin Core is currently near 27 GB, headers-first synchronization should cut down the initial sync time in the next stable release (v0.10).
Thanks for correcting, I didn't know that.
And nice to know the next release of core wallet will cut down on initial sync time.