Hi Toshiaki,
I was recently considering also the Dell XPS 15. Here’s my thread: Surface Book (updated Oct.'16) or Dell XPS 15?
I was also concerned about SurfaceBook and sleep mode since I have also a Surface Pro 4 with those issues. I went ahead and ordered the Surface Book with Performance base (has a GTX 965M card). I told the Microsoft store staff my concerns, and I bought it knowing that if I saw any issues I’d return it. The assured me that was no problem< I could just return it no questions asked within 30 days.
I’ve had this machine for 2 weeks and it’s great, no sleep issues, about 16 hours of battery life and I charge it every 2-3 days. Wakes up from sleep everytime, no issues. I run it on my desk with a 4K monitor and for Rhino works surprisingly well. The advantage for battery life is obviously that it only has 2 CPU cores, and ‘only’ 3000x2000’ pixels in its display. So if you need more CPUs for rendering you will be better off with a 4-core Dell, at the price of battery life.
I did some rendering tests with Octane as it’s pretty good. I’ll post results + Holomark scores on my thread.
…but if you still want the Dell I think you will have a great machine with the 15". 4K seems a bit overkill for that size but 1080p is probably not enough for a nice display.
I hope this help, but probably adds more confusion 
G