If I had to make the decision again, I'd definitely get the M3800 instead of the XPS 13.
1. Google about trackpad configuration (palm detection, etc.) on the XPS 13 Dev Edition, it seems to be a combination of the hardware and Linux driver support. Maybe it's fixed in this new rev, I'm not sure.
2. There are known issues with audio popping and crackling when you plug the XPS 13 Dev Edition into speakers.
3. When you're sitting in a quiet environment, like a home office at night, you can hear electrical noise coming from the laptop. It's a known issue, maybe it's resolved in this new generation.
4. One of our XPS 13s was DOA. It happens. It took eight weeks to get a replacement, starting from the first time I contacted support. Once I was connected to somebody in USA on-shore support, they were very helpful, and told me much of that turnaround time is based on their suppliers.