I can only speak for my own approach, but there's a reason I have many choirs...choice. The choir I use for a composition depends on what I'm writing and what other libraries are being used as well. Every choir library has both pros and cons. Not everyone has the luxury of choice though, so it's really important when choosing the first few choirs to pick ones that you feel at the time will best help you meet your goals. I know...that is obvious, but nevertheless worth repeating. One choir I can suggest you check out is Genesis childrens choir by Audiobro. It's a keeper. There are many choirs that can do epic. Dominus is worth considering for sure, and will be developed further at some point. The Virharmonic choirs are very versatile, and Soundiron Olympus series has many useful features. Venus is my favourite Soundiron choir. I certainly don't envy the decisions you have to make, but hopefully you will end up being happy with your choices.