Different between list & document library

Lists:

Can have attachments(Not indexed), Have major versions only, Do not have Check-in/Check-out features, Not have document set, No open with explorer, No folder, List content Type

SPAttachmentCollection.Add(string, byte[]) only accepting a byte[], means the attachment must fit entirely in one continuous block memory

Libraries:

Cannot have attachments (files are directly in the library), DocumentLibrary Content Type

Have both minor (draft) and major (published) versioning

Have Check-in/Check-Out, Publishing Libraries can use Page Layouts

Have Unique Document Ids out of the box, No 'Read Access' setting, 

SPFileCollection.add(string, stream): means the content can be in memory, a stream, disk or even a TCP/IP socket.