Pros are the diversification of the risk of any QOZB failing compliance and the added flexibility that might be necessary when reallocating funds between QOZBs. It's also simpler to have all your ventures in one holding company. However, the downside is that if a large QOZB fails, it might affect the other QOZBs indirectly because the parent could fall short of the 90% test. There are also niche liability protection concerns that I don't think are material, but they could arise in narrow circumstances. Practically speaking, you need all the QOF owners to desire the same QOZB investments in the same proportions to do a single QOF; instead, it's easier to set up separate QOFs if you end up mixing and matching investors between QOZBs.