What is best way to develop app for Windows 7, Windows8/8.1 and Windows Phone 8.1?

What is the best way to develop an app that needs to run on Windows 7, Windows 8/8.1 and Windows Phone 8.1?  My ideas are:

1. Create a Portable Class Library  with a separate project for each environment that contains the UI elements and uses the PCL for data access and business logic;
2. Create a separate application for Windows 7 Desktop; the create a Universal App for Windows 8/8.1 and Windows Phone 8.1.

Which is the best. My experience with PCLs is not positive.  They are very restricted.  But I hate to duplicate code.

Is there a better way.

Dick

Dick