Modric will suit us 10x better than Nasri. Modric knows how to play in the center of midfield with one other partner. He knows his defensive duties and still engages in dribbling and cutting through defenses. He is an awesome player, but we will not sign him due to the fact that -
1. Tottenham do not want to sell, they do not need the money and Modric is under contract for another 6 years!
2. Modric wants to stay in London.
Nasri is a good player but I see him more as a attacking midfielder, he likes to dribble and storm up front and with a 4-4-2 this could leave us exposed. Limiting him so that he stays back is an idea but look at Anderson, it did not really work with him. We signed Anderson as a AMC but turned him into something completely different.
With this being said, I would still welcome Nasri, for £20M you will be hard pressed to find another player with his quality and experience in the PL for that price.