Midfield crunch
It's often said that winning the midfield battle is key to winning any football match.
It may be a cliche, but is a valid point nonetheless. Arsenal's midfield has enhanced this season, with the addition of Torreira, and the development of Guendouzi. Granit Xhaka, being freer to play in his natural role as a deep-lying playmaker, can thus bring the ball forward more, and not be as concerned with pressing and ball-winning. This superior midfield balance that Arsenal possesses, compared to previous seasons, is a factor in their current unbeaten run.
Spurs, on the other hand, have a good midfield balance tried and tested over several years. However, Mousa Dembele isn't available due to injury, whilst Sissoko despite initial detractors has started to perform well. The styles and structures of either midfield are similar, and who can press more, or retain the ball to a higher degree, will be a factor in victory or defeat.
Torreira, Sissoko, Guendouzi, Xhaka, Ramsey, Dier, etc. will all hold a key part to play in creating chances, limiting the supply from the opposition, and retaining possession. Who does this the best may win out in the end.