I'll be going for the XPS 15 too. I've been using an XPS 13 9333 from 2014 with 8GB RAM and recently I've struggling to keep things under that limit.

The XPS 15 has the advantage that the RAM is user replaceable, and as I understand it, the 16GB model comes with a single 16GB module, so should be fairly cheap to upgrade to 32GB yourself if you'd like to save a few $ initially.