For the time period in which the novel is written, marriage had more to do with social status and money than it had to do with love. Love was more of a bonus if you were lucky enough to find it. Many marriages were set up with the help of the parents if necessary because the daughter was to remain in their household until she married. Plus, the parents wanted their daughters to marry well so they would be better supported in their old age; and, women wanted to marry well in order to live a life of comfort. Since it was not a high-class characteristic for women to work outside the home, marrying well was very important to those seeking a higher lifestyle.
Hence, Linton offered Catherine more as far as her standards were concerned and those of society. He had an estate, a happy family, and the ability to present her to society in the way that complimented her rather than "degraded" her. Truly, she made the best, most rational choice by marrying Linton. She just didn't bank on the other obstacles that would follow her from her childhood. Which brings up a few other themes that come into play in the novel. To check out other themes that go along with this one, click on the enotes link below. :)