One way to look at it - embedded Linux starts with desktop Linux & ditches the parts not needed for embedded systems (is this actually true?), whereas eCos is designed from the ground up for embedded systems.

Now, assume an ARM processor, probably ARM 7 - does performance make a difference? Actually, we talking a very low load system, max 500 transactions a day.

Any advantages of one over the other (or FreeRTOS, etc)? Stability, maturity, performance, development tools, anything else?

All that I can think of is that if I am certain that I will never port to another o/s, then if I go with embedded Linux, I don't need an o/s abstraction layer to allow me to do unit testing on host (desktop Linux box).

Any thoughts or comments? Thanks.