I know too many little girls who are being named Owen, so I'm beginning to associate Owen as a girls name (like Whitney, Carrol, and others before that used to be boy's names). So I would vote for Jacob.
It's a little discordant to the ear because Aiden is Celtic, and Jacob is middle eastern (Yay-cob -phonetically- being an old Jewish name).
It really is an ear thing though. Just as an example, take the top 100 Irish names, and nearly every one "flows" better to the ear with the Gaelic name Aiden:
Conor
Sean
Jack
James
Adam
Michael
David
Aaron
Daniel
Dylan
Shane
Cian
Ryan
Luke
John
Eoin
Mark
Patrick
Thomas
Jordan
Liam
Jamie
Stephen
Matthew
Oisin
Nathan
Robert
Andrew
Darragh
Ciaran
Joseph
Dean
Kevin
Evan
Jason
Brian
Niall
Ben
Paul
Christopher
Eoghan
Cathal
Ross
Joshua
Ronan
Lee
Darren
Peter
Craig
William
Jake
Anthony
Alan
Colm
Cormac
Samuel
Alex
Gavin
Killian
Kyle
Cillian
Padraig
Richard
Ian
Martin
R.
Brandon
Alexander
Aidan
Harry
Karl
Gary
Kieran
Keith
Benjamin
Ethan
Leon
Philip
Callum
Colin
Edward
Gerard
Scott
Brendan
Owen
Dillon
Jonathan
Sam
Barry
Eric
Shaun
Daragh
Donal
Diarmuid
Lorcan
Tadhg
Cameron
Fionn
Neil
Reece