Both are correct, although, as I understand them, they have slightly different connotations. When we use 'constantly, forever and always + present continuous' it implies something happens too frequently and we dislike it/ it annoys us. Examples: She is always arriving late. Tim is constantly leaving dirty clothes on the floor. My cat is forever licking herself. -In all of these examples I am giving a very negative impression. Whereas, it is not always the case in the present simple. For example: My nephew constantly carries his toy car with him. Carey constantly checks her emails. In these sentences, I am emphasizing the frequency but I am not expressing annoyance.

Hi Egor, I think the answer is that either is correct. They both sound right to me! I'd also gently point out that your final line should be 'which one is preferable', not 'more preferable'! I hope that helps.

I'm not an English major or teacher but, I'll try to help answer your question :) As you know, the use of the adverb expressing how the "action" or verb is being done. The adverb "constantly" is expressing the action in motion. So the present progressive pairs nicely with the adverb: I was "constantly sneezing" around my boyfriend's cat. David is "constantly checking" his phone while we chat. I hope this helps :)