Yoga is not the same level as X1C9. I think in terms of build and ranking in the respective line ups, the XPS is probably Dell's parallel. There are things I like about either the X1C9 and the Dell, but in terms of aftersales, Lenovo onsite/Premier has the edge - had bad experiences with Dell onsite for their corporate laptops. Lenovo's Yoga service is not on the same level as their Thinkpad (consumer vs corporate differentiation, so I rate Thinkpad service higher). For Lenovo, avoid going into the Depot service - have heard and experienced bad things there.
As for the machines themselves, the XPS is more modern looking, whereas the X1C9 is the classic laptop aesthetic at under 1.2kg. Personal preference here, imo.
The LG Gram is interesting - while not a business class laptop, it's incredibly light portable and quite well built, so it's a viable option for me. No experience with aftersales service, so it remains unknown.