writing log files

dear BBB experts—I am building a data logging application. this means many sequential writes and flush to disks, many reads, few deletes.

is the built-in 4GB storage suitable to writing to very often? is it better or worse, less or more robust (, faster or slower), than SD level class 4 or class 6 cards?

I believe the standard angstrom distro reads the OS into a RAM overlay filesystem to avoid IO.