It is huge compared to the 13 inch, and absolutely massive compared to the SP4.
Performance wise I haven't noticed much difference between the 13 and 15 inch models yet, then again haven't stressed it out either. Still getting it set up.
Afy - I got my 15-inch, 1TB about 3-4 months ago, and I absolutely LOVE it. I also have the Surface Pro 4, i7 - and I use them both daily. I am really enjoying the 8th Gen Processor and the NVIDIA GeForce GTX-1060. I have installed Microsofts' Forza 7 Racing Game, maxed out the Graphics to 'Ultra' and ran it for hours on my Samsung 65-inch. It runs flawlessly and the Xbox Controller makes gaming awesome. Let us know how you like it after you have had a chance to stress it and break it in.
I'm a few weeks into my sb 2 15, and it's the best laptop I've ever owned. Really loving it. My son's company just made him move to a MacBook pro, and he hates it.
For all the bitching about the dock for the SB, the Apple dock cost him over $200 and it doesn't charge the laptop at all.