If someone has daled minim and one of the minim is not “mehudar” does it then “take away” from the hidur let’s say of the other minim. That because this one is not mehudar it can no longer be called “mehudar daled minim”. Al derech zeh if someone has the option to buy one min that is mehudar even though the other ones won’t be is there an advantage in this?
This might depend on whether or not we view each of the four minim as individual mitzvos or not.
Although the Lechem Mishnah writes that according to the Rambam, one can fulfill the mitzvah without tying the minim together, and this indicates that they are separate mitzvos, the simple understanding is that these are not separate mitzvos, but rather one mitzvah.
Therefore the absence of hiddur in one min does detract from the hiddur of all four. Nonetheless, there is still an “inyan” of having a hiddur in as many minim as possible, for each of them makes the mitzvah more mehudar, even if the hiddur remains lacking due to one of the minim.