The effect of altcoins to bitcoin is pumping the value and popularity of bitcoin. While new coins come into this crypto world first they should base the value of their coin with the value of bitcoin. Commonly bitcoin will be more well know by the team and by the new investors with it. I think the effect of altcoins to bitcoin is more about advantages. I can't see any disadvantages for that. It will be good for bitcoin to have another new coin that enter to it's reign in crypto.