If your idea is to develop software, one big advantage of (most) commercial eval boards is that they work. So when your program doesn't, the fault will most likely be in your software.

If you've breadboarded something, or built your own circuit board, and the program doesn't run, then you've got to debug everything. How easy this is depends on what tools you have available.

This question of what's wrong increases in magnitude if you've built your own programmer too. Use ISP or a commerical programmer.

Dennis