Spurs might not have their manager much longer unless they back him with transfers. He's mentioned this numerous times.
United are rebuilding and there's going to be a lot of opportunity for players to break into the team. Can't say the same with Spurs.
Whom you would or wouldn't join is simply not relevant.
Ole has spoken of his vision, I'm sure that any potential signings will be made aware of that. Develop our own players, firmly advocating youth etc. I'm sure there are many young players who's give their left one to join United. By the looks of it we've already signed up 2 teenagers this summer already. Plus there's the United factor, joining a truly great club with a fantastic history of winning, something Spurs sadly lack and Ryan wasn't born the last time they won anything major