I felt like pointing out the original question was rooted in the concept of what does everyone find to be more "fun".
Not so much which is better by whatever metric.
An assault mech is bigger, has more firepower and armor than a medium mech. But I often have more fun with medium mechs because that extra mobility opens up some gameplay options and tactics options.
But that person who loves assault mechs.. that's fine. I don't object to that, it just isn't as "fun" to me, personally.
Translating that into this discussion. If you love the Titan, rock on, if you love the Castrum, rock on.
I feel like the original poster was trying to evaluate if there was a category that the players overwhelmingly found to be more fun. The evidence so far suggests it really is a mixed bag that comes down to individual preferences, which vary a lot.