Still parsing this... and just thinking out loud. BTW, I indicated SPY Wednesday in my previous post, but I meant to say SPY Monday expiry. So the coming SPY Monday 435 Calls 0.99 Delta vs the 442 Call's 0.43 Delta: Pertaining to what you are calling the "real question," it sounds like 1 x 435 Call would/should be equal to 2.5 x 442 Calls. But since you are getting 5 x 442 vs 1 x 435 for the same money, from my limited understanding, I would say the 442s are preferable because you are getting more bang for the buck.
Hm... Thb, I don't see any reason to use options if you're after delta. In this case, just trade the stock. If you're after convexity, use options and you want max. gamma without paying too much theta for that. Regarding risk, I'd use a delta number plus max $ ammount to buy the highest gamma/theta option. But what do I know, daytrading options is probably not the best idea when you look at the risk premium aka. IV over RV.
For this process, should I trust more on the real ATM rather than leaning on the 50D? (still figuring how to quickly discern the highest gamma per unit of theta). And thank you for sharing such valuable insitghts.
he should write a differential eq to model the gradient change of gamma to theta as strikes change and then seek to to find the local maxima.