In reverse order ...
2) The BH-5 has the same coil design as the TFA-2004Jr, but different construction and materials. I haven't done a careful listening comparison, but based on what I know of the details, I expect the BH-5 to sound a hair better, even though it will likely take a bit longer to burn in.
1) Hard to say what constitutes "worthwhile"! I have always liked the -2004 sound, and the larger core is more important in the all-nickel construction - it's the choice I'd make. Whether the differences are audible, and match your desires, and are large enough to be worth the cost and effort, is not an easy question.
