Warren Buffett and Bill Miller seem to have contrasting opinions on Bitcoin even though both these gurus have endorsed value investing principles.Investors should not turn a blind eye to Bitcoin's progress in the last few years.Even though Bitcoin bulls seem to be convinced of the cryptocurrency replacing the dollar as the world's reserve currency, this is very unlikely to happen during my investment time horizon.Bitcoin, however, does not need to become the world's reserve currency or at least come close to doing so to deliver stellar returns to investors.Investing in mining companies with poor balance sheets is not the right way to gain exposure to Bitcoin.