First off, that wasn't what you said, you said play a 1080p video, not play a video at 1080p, but I'm confused...
The SP3 resolution is 2160 x 1440
A 1080P video is 1920x1080. So you're apparently using 1080P to run your 1080P video and you're using 240 x 360 to work on your Powerpoint and Word. That makes a whole lot of sense. Unless of course you're running video in the background (which is largely pointless). If you told me your were running it on a second screen (which will probably be your next excuse), that would be fair enough, but I can airplay to a separate display and still run the 2 applications in parallel while sending video to a separate display so it's the same. That said, if I am somewhere with a second screen, I'd being using a much more powerful machine than SP3, SP4 or iPad Pro so the argument of second screen essentially kills the benefit of tablet argument.
Now, if you don't have a separate display, you're stuck with having a whole heap of apps that constantly go over the video window which is also largely annoying and useless, so my guess at this point is that your original argument is partially mute because both options have pros and cons, and right now, I can still work on two apps and play video on a single screen with less headaches than you can.