Gold becomes cheaper, more expensive Bitcoin vice versa.
Not necessarily. It all depends on what time frame you are looking at. If you look at the years from 2012 till late 2015, then Gold has gone down in price significantly, that's right. But if you look at the current year, then Gold is doing a very decent job. It's up around 20% this year, and the year isn't even over.
Gold becomes cheaper, more expensive Bitcoin vice versa.
The same applies for Bitcoin as well. It depends on what time frame you are looking at. If you look at the time between very early 2015 till now, then the price has gone up considerably. But that doesn't mean it will continue doing so in the next years as well. Perhaps the next years will show a slow decrease in price. We don't know.
I think this is the main argument to make the right choice. I invest in Bitcoin.
If that's according to you the reason to invest in Bitcoin, then go for it. Always do your own research instead of taking advice from others for granted.