Progressive Streaming - Introduced in Flash 7.0, this method is a low cost yet effective one for the user. An interface or video player in SWF (Flash File Format) is embedded in the HTML/Php/ASP page. This video player contains the required code to playback a FLV file from a server location. Obviously the FLV file is externally placed. The video plays as the file is downloaded and the user need not have to wait till the whole file is download.

Pros -
1. No streaming servers are required based on monthly fees.
2. Consistent high quality playback at any connection speed.
3. Limited technical support required.
4. Easy to setup and maintain.

Cons -
1. You cannot seek forward through the video before it is completely downloaded. You need to wait until the video is downloaded before you can navigate to a particular portion of the video.
2. Because the file is downloaded, the media physically resides on the viewer's machine. Savvy users will be able to access their browser caches or temporary Internet files and retrieve the video.

This is not necessarily harmful if you have no concerns about rights management for the video. But in case you want to protect your video, then this method of streaming is definitely not for you!

Flash Comm Server - Also known as Flash Media Server, or rtmp Media Server this method is more professional way of serving streaming video on web. While in progressive download the file is downloaded to the viewer's machine and played back at the same time, in this method the file resides on the streaming server and is not downloaded while it is played. Apart from that there is no apparent difference between progressive download. The advantage of using Flash Comm Server are twofold. First, your media is protected from thieves. Secondly viewers can seek to any portion of the video to view that portion. This is particularly helpful if you have long hours of training material on your website.

Pros -
1. Ability to handle huge user load.
2. Immediate random access to different parts of a movie.
3. Video remains on server (cannot be saved by viewers).

Cons -
1. Not easy to setup for the average person.
2. Monthly Fees and much costly than progressive download.

Which should be your choice?
If you are looking for a low cost effective solution to put videos on your website and you have a low to moderate traffic then progressive download technique is your best option. If you have a pretty heavy user load BBC or CNN and you are concerned about your media rights then you definitely need a streaming server setup.