It is really splitting hairs when you get into custom actions. Both of those mentioned are very good actions and equally capable of match winning accuracy. I decided on the Stolle Panda because it has a flat bottom which makes for a large, solid bedding area and contact with the stock. Whether or not anyone would really see the difference is hard to say. Many bench rest matches have been won by the Nesika.
Jerry Stiller makes a very nice custom action that comes in several varieties. He makes what is essentially a copy of the Panda but with a more refined firing pin system. His actions are the most affordable of the customs, costing $850 and that is with custom rings and trigger guard.
Any of these will serve you quite well.
Good shooting and keep 'em centered.