i currently have an NES classic but not an actual NES and i was curious to know if there are any drawbacks to using the NES classic over the original?

There's two things that I can think of:

1. Framerate:

The framerate is slightly lower on the NES Classic than on the NES, so your times will automatically be slower when using the NES Classic.

2. Input Lag:

Since the NES Classic has an hdmi input (iirc), playing retro games like smb1 on a hd tv results in input lag. I'm not exactly sure why. Input lag means the amount of delay there is between you pressing a button on the controller and the character moving on the tv. BUT, for players that have only played on hd tvs won't notice anything until playing on a crt.

ok thank you.

Since it's only a 5 minute run, the framerate wont matter that much when you're starting out. But at best you can probably get a high 4:59 with practice on the classic.