I'd reply as a viewer. Calls to action may be a powerful tool for getting me subscribed to you, but it also may be a reason to stop watching your video immediately.
If your video is very entertaining/helpful and you do call to action AFTER I realize its value - I'll consider subscribing. But before that I will see what other videos you have on your channel, and what videos I could expect from you in the future. IMO, that's why it's important being consistent with your videos.
But what if you give me a call to action before the video even starts? Well, if I was searching for a how-to video or the topic of the video is VERY interesting for me - I will jump right to the content, skipping call to action. OR I will close the video immediately if I had just a slight interest to watch that (like, attracted by an interesting thumbnail or title).
Create great content first, and you'll gain more people subscribing to you! (that's what I am learning to do now)