I have also experienced both. DD1 was given the DTaP at 2 months, the last vax she was ever given. I went against my better judgement and did the vax, it was the last time I did not listen to myself. She had a "mild" vax reaction, high pitched screaming for hours, then she slept for almost 2 days straight, barely waking to nurse. Very abnormal for her, the child never slept, not even as an infant, and I couldn't wake her after the vax. I don't know what DD1 would of been like without the vax but I do think she would of been very different. She suffered from many food allergies for years, had a diagnosis of sensory processing disorder, along with other issues, and is just different.
DD1 just shy of 4 when DD2 was born, DH had pertussis when she was born, we just didn't realize it until she was a week old. It was too late for her, she had been throughly exposed by then. I won't sugarcoat it, pertussis in a newborn was hell. DD2 was very sick for a long time, she struggled with health issues, poor weight gain, low muscle tone, she was delayed for a while, and she was completely dependent on O2 until she was 7 months old. Today she is almost 2 and is doing quite well for her health history, she is very sensitive to illness. She catches every bug known to man and everything goes straight to her chest, she uses inhalers.
Pertussis in DD1 was only annoying, she would run around, cough, vomit, and go back to running around. I wouldn't be concerned with a child over year, really 6m. I totally agree with the poster that says pertussis rarely kills. The most dangerous thing with pertussis in a young baby is either a secondary infection or that the baby doesn't start breathing again after a coughing fit. SA really helps, and we used it for us. I will never vax for pertussis. I am pg with #3 right now, and yes I will be wary of pertussis with a newborn, but we also can't live in a bubble either.