At least in my opinion article writing is a whole different breed of cat... And if you want to be a copywriter then be a copywriter-- not an article writer UNLESS it deals with "How To Be A Copywriter".
Copywriting has far more in connection with general marketing principles that it does with composing articles, yet I see many people ignoring the whole marketing enchilada.
We've had supposed copywriters (who were nothing more than articles writers trying to break in to the copywriting game because they smelled far more income than what writing articles will garner) who didn't know shat from shinola when it comes to the mathematics side of the business.
I think all you do by trying to keep you toes in both ponds (copywriting & article writing) is cut your potential for higher paydays.
I don't know of many of the top copywriters throughout history that were also active article writers-- outside of the those relating to copywriting, marketing, business opportunities and self improvement. I guess Denny Hatch comes to mind as someone that is recognized as a top-copywriter who also does articles-- but he's in his 70's now and many of his articles do reflect a business, marketing or copywriting spin.