Ubuntu – What are the differences between different releases of Ubuntu

If you are familiar with the way Microsoft Windows manages its versions, you can relate point releases to Service packs that are released after a while when the product is released to the general consumption.

The basic idea for having point releases in LTS versions is to ensure that the LTS version works on newer hardware and doesn't necessary have to download a huge amount of updates when freshly installed.

The point release essentially contains the bug fixes the version has gone since it was released to the public, which includes security fixes, package updates, translation packs updates, etc.

You can read Mark Shuttleworth's blog, where he talks about the point releases of 8.04. An excerpt from his blog that is relevant:

These point releases will include support for new hardware as well as rolling up all the updates published in that series to date. So a fresh install of a point release will work on newer hardware and will also not require a big download of additional updates.

If you really don't know the difference between those two, I think you really shouldn't be using Ubuntu+1 after all. (quoting aking1012)

Daily builds are updated pretty live with changes in the main packages that are installed by default.

Alpha / Beta are snapshots of Ubuntu+1 in development. They are generally tested for issues in ISOs (but doesn't guarantee you anything, really). So you are better of using Alpha to install if you are hoping not to run into issues when installing.

Unless if you are really low in bandwidth and cannot afford to update after installing Alpha, you should just install Alpha. Then again, if you are low on bandwidth, updating Alpha would cost you more on bandwidth as well.

Just a closing pointer: If you run into issues with alpha / beta releases (which happens quite often), we can't help you much with the issues.