Which is preferable: Shabbat clothing or new clothing during the year of mourning

In mourning within thirty days, when one's weekday pants are torn, and one has the option to either wear Shabbat clothes on weekdays or buy and wear new weekday pants, which is preferable?

It is preferable to wear the Shabbat pants.

Mishna Berura, Siman 551, S"K 44: "And in a place where it is customary to press clothes, they are considered pressed and forbidden even if they are old, as pressing makes them like new, and it is forbidden to wear them during this week. For this reason, it is customary to forbid wearing Shabbat clothes on Shabbat Chazon, as although they have been worn for several Shabbats, their pressing is still noticeable and they are considered like new." Thus, the Mishna Berura holds that the prohibition of wearing Shabbat clothes is because they are considered like new, and therefore it seems clear that truly new is more severe than clothes whose pressing is noticeable. (If one gives another to wear the new weekday clothes, it should be discussed whether it is considered better than Shabbat clothes.)