Re: common design
The pros for that is that it saves money and cuts a lot of regulatory red tape. The cons for that apply to any universal solution: If you find a problem later, you've got it in spades across your entire system.
In the long run, multiple solutions allow the evolution of the best ideas. As one example, note this link from robvg's post below. Note also that these ideas are attracting private investment.
There has been a huge amount of innovation in the energy industry, including oil and gas. If market forces were the prime mover, natural gas would probably be in the ascendancy right now. The wider the range of research and development in ALL forms of energy, with profitable products as the goal, the better off we'll be.