As a group, spin-offs outperform. However, it is difficult to buy all spin-offs as they happen. It may possible to do better than the group by correctly cherry-picking the "best" spin-offs.
However, it may be easier to outperform the group by simply avoiding the "bad" spin-offs.
To spot a "bad" spin-off, look for the ways that dumping a division can disproportionately benefit the parent. Is the parent company overloading the spin-off with debt? Is the spin-off in a low-margin or secularly declining business? Is the spin-off company involved in liability-laden activities?
What do you try to avoid in spin-offs?