Coding for Embedded Linux is considerably different than coding for a microcontroller not running an RTOS or Scheduler.
Even coding for an RTOS capable of running on the LPC2148, it lacks the necessary resources to run Linux, there will be considerable differences.
I have both the BeagleBone Black and the Raspberry PI, I prefer the BeagleBone Black, although I suspect online support through forums and blogs is most likely greater for the Raspberry PI.
One issue with the Broadcom BCM2835 ARM Microcontroller used in the design of the Raspberry PI is that full documentation for the device is unavailable unless you are vetted by Broadcom and agree to sign a nondisclosure agreement.
On the other hand, all documentation is readily available for TI Sitara AM335x ARM Cortex-A8 used in the design of the BeagleBone Black.
There are other reasons I prefer the BeagleBone Black, however if you are just getting started in the Embedded Linux realm, it might be more advantageous for a beginner to choose the Raspberry PI due to the extremely wide range of support.
The Raspberry PI has become sort of the Arduino of the Embedded Linux world.
BigDog