Well there is no contest here.
Proprietary design allows one thing : to be exclusive. This means that your customers will obligatory come back to you in the case they want upgrade or need to solve problems. So in order to make this more acceptable, the manufacturer must go beyond standard existing parts.
For example Apple has been manufacturing Macbooks for long time and these were at some point the slimmest products available. Same goes for screens, Retinas were the Shit not long ago. Now the industry has caught up and this doesn't mean anything anymore, all comes down to preference or "préjugés".
Standard products must imply two things : easy reparation and customization must be available, also it must allow access to the best of standard components used in other applications.
In the end it also comes to the industry's evolution. If there is a growing request on a market, manufacturers will rise with products to answer the request. Where one is exclusive first, he just becomes one part of many when the rest of industry catches up. And where others have set standards, the proprietary one is no more competitive Unless he can overcome the mass with new exclusivity beyond standard.
Proprietary designs are bound to become obsolete where standards are bound to evolve.
My conclusion would be that it is best to try and mix best of both worlds, improve standard to the highest level like proprietary design could offer.
