What are the pros and cons of forced marriages?
By "forced" marriages, I assume you mean arranged marriages. (I cannot imagine any benefit whatsoever to a forced marriage.) The advantages of an arranged marriage over a "free choice" marriage are many. Couples who marry this way have much more reasonable expectations than couples who choose their partners on their own, and consequently, are generally much happier in their marriages. With a partner of one's own choosing, in Western cultures, the partner is expected to be the perfect everything, and of course, that is not a realistic expectation. Arranged marriages also have all the power and resources of family, community and culture behind them, shoring up any shaky moments in the marriage. Generally, in cultures where arranged marriages occur, divorce is more difficult and thus, couples tend to work out their problems. Certainly, the divorce rates are strikingly lower than in countries where there are no arranged marriages, as you can see by clicking on the link provided, which also has other interesting information on the differences between these kinds of marriages.
I recently had a student in an arranged marriage. She and her husband are quite happily married and have grow to love one another deeply. We had an interesting discussion in class one night on this topic, and one thing that was clear to all of us was that in a culture in which marriages are arranged, people do not usually regard this as bad, and in many cases regard the arranged marriage as a positive cultural phenomenon. In fact, the idea of choosing one's own partner on the basis of falling in love was a deeply alien concept to my student.
The disadvantages are likely to appear when people are so incompatible that their families and communities cannot cure the problems. Such incompatibility can take various forms. One might be age and another might be socio-economic, although most arranged marriages take place between partners of approximately the same socio-economic status. From the Western perspective, the idea of not having a choice is deeply disturbing and offensive, but this disadvantage seems to me to be more rooted in a cultural difference than it does in the concept of the arranged marriage.
If you really mean "forced" marriage, I cannot see any pros. It is surely never right to force someone to marry without their consent.
If you are talking about arranged marriages, there might be some good points. Arranged marriages can be set up between people whose families will approve of one another. This will lessen the possibility of the families disliking the marriage. It also takes the pressure off the couple -- they do not have to be totally in love with one another and they will not expect to be "perfect" for one another. Instead, they may have time to grow to like and respect each other and maybe even to love. This might make for a much more stable relationship than one based on young love and passion.