The bulk difference doesn't matter, because the typing on Delphox is so terrible and the bulk so below average-average that if you're choosing to use Delphox for defensive reasons, you're choosing it for even wronger reasons than usual. You take neutral U-turns, so good luck switching in on a smart player with scizor (who most fire types wouldn't blink at). No immunities, which is a big thing for a pokemon with those defenses and which needs a pretty ready set of switch in chances. You choose Heatran and Volcarona if you want a fire type that can take hits, not Delphox. Volcarona, by the way, is far better than Delphox at CM sweeping in OU, because his CM boosts his speed as well.Plus he's more powerful and has recovery. And if you compare delphox to other psychic CM users, the latis are humilioated that you're even comparing Delphox to them. When you talk about Delphox being that high and powerful, you don't compare his CM to Chandelure, you compare it to Volcarona and the latis. Once you start getting lower, timid base 80 on Chandelure outspeeds all the important things that need outspeeding, plus his set of immunities in a metagame currently rife with blazikens and lucarios is far more useful for setting up a CM. Plus no garchomp is going to be switching in on a +1 delphox, man. The other, many pokemon that completely wall delphox will. Garchomp will switch in maybe after something is dead, and then good luck.
No. You should really just look these things up.
You keep talking up that 104 speed like it's the end all be all, but it's really just minutely above average. delphox is probably one of the most predictable pokemon around. And it's hard countered by many of the top pokemon in OU. A slightly above average speed, small movepool, terrible typing, and mediocre bulk do not make a pokemon good, especially a pokemon outclassed by just about every other fire type. If above average speed and good offenses were the requirements, Sceptile would be OU. He has better + stronger coverage, unpredictability (dat unburden physical set, man), better defensive typing, and higher speed, plus he's not trapped and walled as easily as delphox. But he's down in RU.
There's a reason, and that's V-create. Because V-create is so damn good. But that doesn't mean that Victini can't run specs or special sets. Like I said, if people really needed a special choice pokemon that was pursuit weak, had middling speed, and fire stab, then people would probably still use victini, because he has better coverage moves + higher stab + U-turn. The offensive stat difference doesn't make a difference, because Victini does more damage due to the higher BP of his STABs and coverage. Plus he can run one slot V-create, so the blobs don't wall him. Plus he can u-turn out pf predicted Ttars. Delphox has none of that (and he's far bulkier than Delphox, if you're really that set on using Delphox because it's "bulky").
And good luck running that delphox on your sun team come december. Once heatran and the latis are running around (all three of whom drop sun teams like a bad habit), that delphox is going to be deadweight. Sun teams need every teamslot they can get, and Delphox does nothing any other pokemon doesnt. Infernape won't be much better, but at least he hits Heatran.