The thing is. TS3 had a more complete base game than TS4. So when he says s4 has more dlc, it's because the game's playing catch up to the previous installments while doing it's own thing.
So like, patches added ghosts, swimming pools, family trees, basements, dishwashers, repairmen, gardeners, nannies, toddlers, and probably some others. All of which were available in the s3 base game.
Sims 3 Ambitions gave us 5 professions and laundry. Get to Work came with 3 professions and laundry is in a separate pack. Sims 3 Late Night added vampires, the butler and celebrities, which are separated into 3 different packs for ts4. The laptop was added in ts4 StrangerVille but available in ts3 base game.
I want to say the bigger team has to do with engine and graphics stuff. Are things more in-depth when they separate it in ts4? Sure, kinda. BUT ts3 still gave more with a pack.
In a way, it's almost like quality vs quantity. Do we get more stuff like we did in the previous installment or do we get less with expanded features?
Edit because I agree with @RememberJoy that I am willing to overlook everything if I could just get some real personality in my sims