MorningStar's Personal Finance column provides a detailed explanation of why funds carrying a tax loss make better investments. All in all, mutual funds with a big tax-loss carryforward can delay distributing gains and thus help your money to grow more time before being taxed.
Nevertheless, the benefit from tax-loss carryforward is small anyway, at least for open-ended funds, so the article correctly concludes that "you shouldn't use a large tax-loss carryforward as a primary reason to buy a fund. Other things, like experienced management, reasonable costs, and a sound investment strategy are more important. But all things being equal, you'd rather have the fund with the large tax-loss carryforward."