as much as this debate is boring me im going to wade in anyway. Alli has a great habit of popping up and scoring goals but he can be anonymous for 85 minutes of any given game. Grealish on the other hand is constantly involved as play goes through him all over the pitch. They are different types of number 10 as mentioned above with Alli more of a second striker type.
Honestly, with or without my Villa bias, if I had to start either of them in my team at the start of the next season it would absolutely be Jack. And for what its worth I think he would/ will thrive in that Spurs team.
Stupid Spurs