Tony McCoy admits he is facing a tough choice over who to ride in next week's John Smith's Grand National at Aintree.

McCoy has the option of partnering the Jonjo O'Neill-trained Sunnyhillboy, who finished a narrow second in the race last year, or Ted Walsh's Colbert Station.

Sunnyhillboy has had two unsuccessful outings over hurdles this term and was forced to miss his intended prep race in the Cheltenham Gold Cup due to minor setback.

In contrast, Colbert Station has run four times this season, winning over both fences and hurdles, leaving McCoy with the pick of two live chances.

He told the Daily Telegraph: "Sunnyhillboy is experienced at Aintree, having all but won the race a year ago when he was pipped on the post by Neptune Collonges.

"He would be in the half-dozen you would pick that are almost guaranteed to get around. He is well again and I would be confident that Jonjo O'Neill has him at the top of his game.

"Against him is that he likes proper good ground and is 10lb higher in the Handicap this time.

"Colbert Station is, at nine, a year younger. He has won on all types of ground, is much less exposed and I have huge respect for trainer Ted Walsh.

"Against him is his chasing experience, or lack of it.

"He has only run in five chases, but he feels like a natural and won the 28-runner Paddy Power Chase without a semblance of a mistake. That was like a mini-National.

"There are very good cases for both horses and it is going to be a difficult choice."