I'm considering the New Macbook for its portability and sleekness. However, I'm also about to start to try final cut for video editing. Is it advisable to get the New Macbook if I wish to install and use Final Cut?
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Assuming you are asking about the new 12"Macbook retina model that just came out. Short answer = No.
Picking the "right" video editing system, can be a daunting task. Many factors go into deciding what computer will meet your needs, depends on what type of videos you plan on shooting, (SD, HD, 2,4,6K), how many cams, effects, etc… No matter what, video editing is one of the most taxing/demanding uses of a computer, therefore you need the best you can get/afford.
It really does not have the processing power in its CPU, GPU or ram. It is also a fanless design that will throttle its own performance as it heats up, and video editing will heat it up. Finally, it uses the new USBc connector and this port needs to mature.
IMHO, for a laptop, you will be better served with a retina Macbook Pro with an i7 CPU and discreet GPU and include 16GB ram. If $$ is an issue, buy the best you can or consider a used laptop.
If you can get by with a desktop, recent iMacs will all outperform the 12" Macbook "Far, far and away".
The older legacy towers are now getting much cheaper on the used end and can be souped up to really perform quite well. Again vastly faster than the 12" or any other laptop.