There is no perfect ship for all applications, rather there is a perfect fit for the fleet you are building at that time.
The MC30 Assault Frigate is a ship I am trying to get some kilometres out of at the moment, I like the idea of redundant defense tokens, good shields and black dice as a threat or opportunistic attack. It also has a slightly wider side arc and is therefore a good choice in an Ackbar fleet or as a threat to Demolisher. I am also finding that the MC30 works with every commander, whereas the AF tends to benefit from a smaller set of commanders. The MC30 is fast and reasonably maneuverable, so it can keep a ship with no red dice at distance slightly easier than an AF, and that speed allows it to remain in formation with a wider range of ships.
On the other side of things the AF has Squadron and can command squadrons that the MC30 cannot. It also has a better hull and can survive a little better. The MC80 being significantly slower and off the MC30's sweet spot of speed 3 can make the AF a better choice for being in a fleet with an MC80.