When complaining, as it seems to be the case in the sentence above, the use of the Progressive is more appropriate. "You're always smoking in my room!"

Aleh La, thumbs up!

Present Progressive with the words "always" and "constantly" habitually expresses a reproach:
you are constantly chatting/smoking/growning!.... (meaning "i don't like it")

oh, "growling" or "grumbling" (not growning)

Интуиция подсказывает, что лучше употребить "the present continuous tense - ing" . Aleh, есть ли какое-то правило?

Да, такое правило есть. If you want to express anger, annoyance, or complain about one's repeated actions and use words "always, constantly, forever" , the present progressive is more appropriate. "You're always smoking in my room!"
If you just state a fact, than it is better to use the simple present: "He always go outside to smoke."

Ok, thanks.

Here is the link http://www.perfect-english-grammar.com/present-continuous-use.html