Not exactly the comparison you were looking for, but close enough - the real 4.A versus the Flex twin in the micro shell (which may or may not impact SQ compared to the bigger shells): The Flex actually has slightly more perceived punchiness. The 4.A extends deeper but it tends to require an amp or nicer DAP to bring that out of it. The Flex twin has more punch to it straight from an iPad or similar and doesn't really change much when amped. But the Flex can't compete in terms of clarity or top end sparkle. Out of a lesser source, the Flex is actually somewhat more forgiving, which can be a good thing at times.
I think the Flex twin is a really good value for the price, and I'd be happy with it for daily use. Yet it can't compete with the more expensive, more-driver-having 4.A, and I assume the 4.Ai would be the same story. But for your purposes the Flex twin might just be the better choice.