Horner, along with Red Bull owner Dietrich Mateschitz, advisor Helmut Marko and chief technical officer Adrian Newey, are using the current summer break to mull over Mark Webber's replacement.
Earlier this year Webber announced his retirement from Formula One to join Porsche's sportscar programme, prompting furious speculation as to who would fill the vacancy.
Red Bull have narrowed down their options to 2007 world champion Kimi Raikkonen, along with Daniel Ricciardo, a product of their young driver development programme and currently with Toro Rosso.
Asked as to three-times champion Vettel's preference, Horner replied: "I don't think he minds to be honest.
"I don't think Sebastian has any concerns about going up against any driver, and he hasn't voiced a preference either way. He knows Kimi, he knows Daniel.
"Both are very quick drivers and would represent a challenge for him, but he has not looked to influence the team in any way as to which way we should be looking."
Horner has also dismissed suggestions he would find it difficult managing two 'number one' drivers should Red Bull opt for Raikkonen.
"Both drivers get the same opportunity," added Horner.
"It's down to what they do on the track that determines who is the lead driver or not, and the lead driver at any given time is the one who has the most points."
Ricciardo put in a strong showing at last month's young driver test at Silverstone when given half a day in the current Red Bull.
Although suffering a spin when trying to find the limit of the car, Ricciardo impressed with his pace and feedback, leaving Horner and Red Bull with a tough choice.
"Daniel is at the beginning of his career, but he has the speed, and the rest you won't know until you put him in that situation," said Horner.
"But we've a reasonable amount of information to make a decision.
"We obviously want the two fastest and strongest drivers we can put in the car for next year, and both Daniel and Kimi would represent extremely good options."