Not only does the Windows Store not have a good refund policy, but the biggest issue is that games bought via the Windows Store are built on Microsoft's Universal Apps platform. This means you don't get real fullscreen mode, no support for SLI/Crossfire, no capability to turn V-Sync off, no modding support, etc:
To begin with, games purchased through Windows Store are built on Microsoft's Universal Apps Platform, and not the conventional desktop-based executable. The game is essentially a "modern UI" app, and not a conventional Windows application. This has great limitations - no NVIDIA SLI or AMD CrossFire support; no real fullscreen mode (just borderless windowed mode or pseudo-fullscreen); and V-sync being always-on. Other major downsides of UAP apps include no support for modding, and mouse macros. What's more, since UAP apps don't have *.exe extensions, you can't add them to Steam, and so no Steam Controller support. The Store in itself doesn't have a good refund policy along the lines of Steam and Origin limited full-refund policies; and you'll never be able to play your games on Windows versions older than Windows 10.