What is the difference between the snapshot and the non-snapshot?
The non-snapshot is considered a "stable release". It can have issues, but I try to fix any serious ones and release a new version (like 1.4.1 and 1.4.2), but those versions mostly won't contain new features.
In the meantime, I'm developing new features for the next release (currently Tiled 1.5). The snapshots are regular development builds that enable people to benefit from the features that have already been implemented as well as to help testing them.