The output power and efficiency of linearly polarized high power Nd:YAG lasers is limited by depolarization and bifocusing. Both effects degrade the beam quality and decrease the output power. In a single pass configuration, [100]- and [110]-cut crystals can be used to reduce the depolarization. Here, we compare [100]-, [110]- and [111]-cut crystals in an oscillator configuration. As expected it was possible to reduce the depolarization loss by using [100]-cut crystals in our configuration, while the depolarization loss was higher for [110]-cut crystals. The thermal lens establishing in these crystals is not circular, which can degrade beam quality in high power operation.