I saw a post some time ago about how a mythic blaster is significantly more powerful thanks to Mythic Disintegrate. I'm not entirely sure I agree, especially since Channel Power applies to an Intensified Maximized fireball just as well. Let's say you cast that at 13th level.
The channel power maximized intensified fireball does something like 145 damage in a spread, half if your target(s) somehow make their throw. This is most of a CR 13 creature's hit points, and equal to a CR 11 creature's hit points.
The channel power disintegrate deals, on average, 204 damage and maybe some Con damage if it's not immune to that to one target. 24 of that is overkill and wasted, especially if you did enough Con damage to lower the HP per HD. If it makes the save, then it takes half da-- no, sorry, it takes 33 damage and 1 Con damage, which does nothing per RAW on ability damage.
So, if you're facing one CR-equivalent opponent and you're absolutely certain that it won't make its save, then the disintegrate will deal more damage, and more than likely overshadow the rest of the party when you one-hit the bossfight or whatever it was. The fireball makes you look awesome while you take out the mooks or leave the BBEG just enough HP for the rest to deliver a nicely gory deathblow.
What's so great about disintegrate, mythic or not, and more generally, is building a mythic blaster any different than "take Brewer's blaster and slap Channel Power on it"?
Also you can ignore fire immunity (at a cost) with mythic fireball.