The regular centre back partnership at Brentford was Harlee Dean alongside the former Bee but, since the 24-year-old refused to play against Burnley to try and force through a move to the Clarets, it has been a battle between O'Connell and Barbet.
Smith knows the pair are different as players but will be basing his selection on performances, rather than their respective strengths in respect to the opposition.
He said: “They're different as players. Jack would probably say he is more of an aggressive front footed player.
“Yoann would say he's more of a tactical player who can read play a bit more. They've both been doing a pretty good job.
“I don't look at the opposition but more about we want to play and what we need in the team.”
O'Connell was preferred to Barbet against Wolves after the Frenchman's red card at Sheffield Wednesday and, it was the fact he lost the shirt, that led to the young Englishman keeping his spot for Wolves.
Smith added: “It's a battle between Jack, Yoann and Harlee. We've got three centre backs fighting for two positions.
“Yoann made a mistake which cost him a red card. Jack didn't play as well as he could have but he did well against Derby and deserved to keep his place.”