Thanks for the comments all! Good to get other angles on this, from all camps.
For me its about the narrative of the fight, the characters and the why. A Titan or Super Heavy (to a lesser extent) doesn't really feed that requirement for me, plus it can skew a game if a player isn't expecting it. And that looks set to happen more often with Super Heavies becoming more and more a part of regular 40K.
Also, where does it end....
"No, no, no. Titans, thats not 40K, thats small scale and is a side show compared to the huge, city sized ships in space that battle it out. A battle group of 50 Titans, boring, I mean the ships is what its all about, we were playing this one game where a ship exploded so massively it took out 2 planets!"
Bigger is not always better.