Both have tremendous potential but investing in any of them depends on your risk tolerance, investment strategy, and investment capital. With the advancements in technology and going along the race, investments in bitcoin have become quite popular now-a-days.
The long term value of both are good. There will always be these choices to make but the chance of getting the maximum profits is getting both gold and bitcoin without getting altcoins at all.
Even though at this juncture we think that there are one and only investments, getting both is the best possible way for any trader. One going down will always give you calm when the other one remains in place. Be diligent about these things and don't be stubborn about only one asset.