For instance, I heard that if the baby gets his last name, that when they break up and start a battle over custody, that the father will have more leverage if the baby has his name... of course that might be a complete bunch of baloney.
Oh... that's has got to be the "biggest pile of Jumbo (that's what we call baloney in Pgh)" I've ever heard. Women have always and "will" always have for the foreseeable future the most leverage in a custody battle in a court of law - reagrdless of the bay's name.

On a sidenote, when you are about to give birth to your baby, let us hope you are not thinking ahead to the day you get divorced and fight over custody. I know you aren't - just an observation.

I say if in doubt, give them both. My mother-in-law named her son (only son and potential family namebearer) her father's last name and also her married name. Her father was a prominent citizen and local historian and she wanted to carry on his name in her line. So hence, Gary Robert Craighead "Last name". Craighead is still written in his name and he actually goes by the first name Craig. Actually very few people even know his Gary Robert versions - I think is was a surprise to his wife when they got married. I am a traditionalist. I like the woman changing her name and subsequently the children inheriting it.