Honestly it wouldn't really matter for me, but if I had to pick I'd say boy mainly because I'm the eldest in my family and so is my father. Although my grandfather actually has an older sister if I recall.
I will admit a lot of the official G4 pony merchandise were pretty darn terrible especially in the early days, although it did improve a bit towards the end. I really do like the 2017 style brushables I even own several of them.
Not exactly a fan of these their heads are way too big in comparison to their bodies now and not to mention they kinda look like a cross between Littlest Pet Shop and Unikitty. Also Fluttershy looks kinda tomboyish now.