some kinds of enhancement... Which would you choose?

Hi all.

There are some kinds of enhancement in SAP.

(EXIT, BADI, OPEN-FI, Enhancement spot ...etc)

If there are some kinds of enhancement match your purpose, which do you choose?

For example, I'm trying to enhance in MM01.

EXIT: MGA00001

BADI: BADI_MATERIAL_REF

Both of enhancement can be function.

I wonder which is the best...

Which would you choose?

and What is the reason?

thanks.