That is quite safer if you ask me, because those investment projects are not always legit and in such cases you might lose some bitcoins if you invest in them, though you can earn some profits if you invest in trading but that needs understanding and learning.
Yes it is safer. But I don't think putting your coin in the wallet can be considered investing (maybe in some cases). Well I will classify that as holding.
But I don't recommed that since the fluctuation of Bitcoins price is not always going upwards but instead downwards in some cases. There were times when its price is very low. So, you may have a negative profit if this happens and you will not invest that in trading or other legit sites. Of course investing involve the risk of loosing money. If you don't want to loose money. then just stay your money in the bank with less interest annually and loose the opportunity to earn more in trading or investing