[QUESTION] which is better?

i don’t know anything about guitars so I’m hoping someone can help me out here. I’m getting a guitar for my partner for his birthday so I can’t ask him directly but he’s mentioned to me that he really wants a Martin d15. As you know this is definitely very expensive, but I found a Sigma D M-15 that is apparently something really similar for much cheaper. Hes a pretty advanced guitar player so he’d notice if there was too big of a difference in what he was expecting from the Martin one. Should I get the Sigma one? Is it practically the same?