I have both and like them both...Can't beat the healing ld sk gets as he is blasting through a base.
Have scatter on my Skull Knight. Almost threw this 5/5 corrode I rolled onto him, instead kept the Scatter - Life Drain set up and threw the corrode on Rockno.
What crest set do you have on the Life Drain SK?
As it pertains to Skull Knight:
Corrode is better than Life Drain
Corrode is better than Scatter
Corrode is better than Deadly Strike.
Corrode cannot be crested, the rest can. Give your SK Corrode, and not only do you have a strong SK, you also have a lot more flexibility.
Corrode also sounds cooler, looks cooler, and is generally a more pleasant talent to be around.