As others have noted, a "regular" vs. "buyer's agent" really doesn't make any difference.
What, in my experience makes a huge difference, is the effectiveness and knowledge of the realtor. I would recommend finding a very experinced relatively "busy" (popular) agent who has a good administrative support team, knows the local area very well, has worked many years in the local area, and has good connections. My last realtor was excellent - so so so excellent. What she did: she found me the right neighborhood for me (moving across country) after I sent her an exaustive list of the things I wanted and didn't want, she knew many of the houses already having been in them at other times they were sold (she had been a realtor in the area for 30+ years), she was able to help me evaluate which aspects of the house were more important to me vs. me being obsessive, she knew the school districts, she understood negotiating a price and was very no-nonsense about it. And more - by far the best experience I had w/ any realtor (there were other good ones, and one notably bad one).
Personally, I would not hire a relative to represent me in a real estate transaction. If things go wrong for some reason it would create too much bad blood in the family.