Which vaccine is good for children – painless or the one with pain?

Painful vaccines are whole-cell vaccines that are accompanied by undesirable side effects such as swelling, fever, and pain.
The painless variants of the vaccines reduce these side effects considerably including pain, fever, and swelling, but they also reduce the immunity offered by the vaccine.

The effect and the protection provided by painless vaccines lessens quickly as compared to painful vaccines.
Whole-cell vaccines cause pain but offer enhanced long-term protection against pertussis.

The acellular painless vaccine needs frequent boosters as the protection wanes off in some years.
Hence, painful vaccines, in primary series, are the better choice for parents who can manage pain.