Delta is the worst program. I refuse to fly. So they miss out on my 3-5 long haul business class tickets each year.

AA and United are about equal. I give the slight edge to United for being easier to use miles efficiently. AA seems to generally have better flight times/routing to where I want to go.

As far as earning miles. All methods have there place. And all can be used in moderation. That is spend on cc, cc applications, actually flying, misc other methods. If you use a balance of all, you will keep yourself rich in miles without having to go crazy on the cc apps.

As far as credit cards. I agree with your premise. Many on this board will tell you cc's are the way to go. I apply for about 2 per year and my wife does the same. That is enough (with my business miles) to satisfy our free flight/hotel needs (in economy). You are MUCH better to under apply to cc early in life. Some say keep your score above 700. I say 740. And right now I'm at 760-780 as I stopped all cc nonesense as I'm buying a house this summer.

cc's are very useful for miles. But only go for the big offers (if you do). 50k miles minimum. Everything in moderation. Once you get your score above 740 (if its not already), its fine to have a hard pull or 2 a year. (Plus you can spread those around to the 3 different credit reporting companies, but that is probably more info than you care to hear.)