I used a Dell XPS 13 (2013 model) Developer Edition at my last job and use a 2015 MacBook Pro 15" at my current job. The Dell was superb and served me well for 2 and a half years of work with no significant issues. However, my colleague had issues with overheating and resulting unintended shutdowns. If Dell continue their 'Project Sputnik' work I think they will be able to really challenge Apple's dominance as the go to developer machine. I'm definitely not the only person who thinks it's mad that in 2017 the developer community, which relies so heavily upon open source software, is effectively held hostage by the whims and machinations of Apple when it comes to their development OS (and thus, currently hardware too).
My current experience with the MacBook Pro is very good (once I installed several add-ons like TotalSpaces 2 to emulate Ubuntu workflow) but I feel the real reason dev teams are going for this option is the safety in numbers you get from everyone using the same machine which is also used by millions of other developers. It's a bit of a tired expression but the MacBooks do just work.