IMO the perfect diaper bag will greatly depend on your lifestyle. Will you be a SAHM or work full time? Do you intend to go out a lot? Breast feed or bottle feed? Cloth diaper or sposies?There is not one single diaper bag that will have perfect versatility that is why so many brands are thriving or they will all die a natural death.
Above all, I would very highly recommend a diaper bag that is machine washable and dries quickly. As any parent will tell you one of the messiest things is cleaning up newborn spit ups. All babies spit up while being burped and if your diaper bag is closeby it is going to get barfed on for sure. I wouldn't spend a fortune on a diaper bag not just because it might get soiled but because your needs will change over time you will pack differently for a newborn 0-4 mos old vs 5-11 mos old vs 12-24 mos vs potty training, etc. You would probably use a bigger bag for newborns because you will be carrying more diapers, bottles, smaller bags when babies get less needy, and then bigger bags while potty training - portable potty seat, flushable wipes, extra sets of underwear and clothing, then medium sized bags for preschoolers to contain toys, crayons, small books, snacks, etc.
The PPB Cake is stunning! But IMO not really practical since it stains easily (I have one!) and is a headache to clean even spot clean! And not to mention it is super heavy when empty. Can you imagine how it will weigh when full? I'd think the most practical PPB bags are the glazed ones because they can be wiped clean but there are many other brands that have better durability.
Although my last baby is still in diapers I am finding myself moving away from the diaper bag stage

I am loving lighter bags now because sometimes I tend to carry too much.