So a friend made a video that was put up recently, but due to various circumstances I was asked to edit a part out of it and put it back on.

I got the mp4 file he originally uploaded which is good quality and approx 150mb.

The problem I have is after I edited the small part out and render it, I either get enourmous file sizes (1.5gb) or ridiculously bad quality.

There are so many options to play with when it comes to rendering. Has anybody any advice I can use to have decent quality without stupid sizes..... like the original video?

Thanks
Beany

Note: I've been using FCP and after effect on a mac.

Well,

video encoding is always underestimated, there is not just one answer to your question.

I would recommend to export as mpg, or mp4...
But maybe you should ask your friend the specs of the original file. Then export in the same settings.