This is not an easy question. It depends on the type of product you're intending to do. I will share my personal view about this...
When the product is a tablet-like and is intended to have 3rd party apps and a reuse Android apps, Android is my the choice; otherwise I'd use Linux. Android will easy some things but it will also be a "fat system" due the number of abstraction layers it has while Linux allows you to make a much lean system which has exactly what you need, no fat.
Without a clear and more deep understanding about your product, experience and wishes it is hard to make a suggestion.
This will run Apps, with some UART interface to low level hardware and Ethernet for remote control, touch screen interface to operator.
The i.MX53 kit comes with Linux, without Android.
If I start it with Android, where can I get the Android i.MX53 examples?
For this type of system I'd go for plain Linux. It is too simple system with no gain in use Android ecosystem.
We already have a number of Android Apps, this new design will run Android Apps as well, this is why we prefer Android.
Where can I get the Android i.MX53 examples and step by step guide?
Here it is http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=IMXANDROID
But regrettable they have only Android 2.3.7 version based on 2.6 kernel
as for this platform.
I download, and unzip the file, but I can't find the user instructions file .
The user guide is located here: