Downloading From Storefront

I haven't got the best Internet, it's approximately 5mb down and 1mb up. I wanna download FIFA 14 from the store on my xbox. Will it make any difference to how it plays/runs than if I got it on disc?

Basically will it be laggy cos my internet isn't the best

No.

Once you download it,it's the same

Only thing that will be "laggy" will be the time It takes to download it, may be a few hours. Once the game is downloaded it'll run the exact same as if you bought it on disc. As for playing it online I doubt you'll lag.