I own a Dell XPS 12" Convertible, i have the I7 version with 256GB SSD, i bought it in Jan 2014, but i recently switched to 2016 MB and iMAC again (I've used MAC even in past, but i needed more portable laptop so i switched to Dell). XPS is good but still find my MB to be better in stability, security and portability. Now my wife is using my Dell XPS for basic internet browsing etc...
Following were the main problem with Dell or actually windows:
1) I work for multiple company and also have my own company so I've multiple email accounts with some of them having over 100K emails and the biggest problem with Windows is that outlook starts getting too laggy and slow even with i7 and SSD Drives though i don't face this problem on OSX, my MB as well as iMAC both are working very smoothly and are easily able to handle these large amount of emails. MAC's MAIL client is far more smooth and faster then MS Outlook, especially the search works really fast even with such large amount of emails.
2) Battery life - I never got more then 2-3 hrs on my XPS 12 though my MB easily gives more then 7-8 hours of battery life.
3) Portability - MB is much more lighter and slim and hence much more portable then XPS
4) OS Security - I even handle Abuse department for a big Datacentre, so i get all kinds of abuse complains where i've to even visit a lot of malware/virus infected websites to verify if the complain is right or wrong, even since we provide DDOS Protection and other security services we are even target of lots of hackers who tries to send us different malwares/trojans all the time even via email. With windows i was always concerned about security as i might get infected etc... (
yeah i use Kaspersky with windows) but with OSx i usually don;t need to worry about it much. I even use a AV with MAC for security reasons which i don't keep on all the time unless i've to visit some malware infected website to verify it.