It is the same because they are both currencies. It is different because bitcoin is a store of value. It will rise in value in long term. The dollar always drops in value.
I agree with you that value of bitcoin will be rise in long term and i think should invest it but i don't think so that dollar always drops in value. It depends on the condition of the future
From the past experience, dollar always drop in value. This was proved the inflation index. Over any 5 year period, the inflation figure is positive.