There's actually 16 DLC tracks for Mario Kart and they are all amazing. All done the same way has the game so Half is remade old tracks and the other is 100% new. An amazing game for its first iteration in HD! I still play it often enough.
I played 1 cup of the speedway (3 tracks). I haven't touched it again since. I prefer the takeover simply because each character you play with has its own abilities and you get to experience each character's "flavor". In Speedway, everything is the same. You can play with Jack Skellington or Han Solo, it doesn't matter.
That's my opinion... but if you love DI, you need it of course!