Is it better to have derech eretz and to be a Mensch or to only learn Torah?
Maharal defines the idea of derekh eretz (Netivot Olam, netiv Derekh Eretz):
Derekh eretz is comprised of all the ethical teachings in tractate Avot, as well as the ethical teachings mentioned in the Talmud, and all other ethical teachings. It consists of conduct that is proper and that is pleasing to people. It includes teachings which, if one does not follow them, he thereby commits a great sin and transgression, so that one must be mindful of them. This is why they are called "divrei mussar" ("chastising words"), for they chastise a person that he should not walk in the path of evil.
Personification of virtue - one aspect of Derech im Eretz.
In the Talmud and Midrash, there are approximately 200 teachings concerning derech eretz as decent, polite, respectful, thoughtful, and civilized behavior. One representative teaching is that "Derech eretz comes before Torah" (Midrash Vayikra Rabbah 9:3) – one cannot personify Torah until he demonstrates derech eretz in everything that he does. There are many more such teachings in the rishonim and acharonim (post-Talmudic authorities). The mussar literature, in fact, presents an entire body of thought devoted to the subject of middot (character traits) and "behaving like a mentsh" (refined human being). Here, the way that one behaves is regarded as an external manifestation of one's middot. Wikipedia.com
Under the general rubric of derech eretz, the sages caution us against overeating, eating too quickly, or staring at someone else who is eating. Also, one should not talk too loudly or too much, and should greet people pleasantly. Likewise, a person with derech eretz is careful to spend only what they can afford. In order to raise children with derech eretz, it’s important not to spoil them by accustoming them to having delicacies. In general, to have derech eretz usually means to live ethically, responsibly and with dignity, and to be considerate of others.
Sources and ideas were inspired by Harav Amital's essay "derekh eretz -Being a Mensch" and The Legacy by Rabbi Berel Wein and Rabbi Goldstien.