The size difference is rather small with regard to the razer. To your point I believe the razer is a more robust laptop then the current MBP.
In helping my purchase decision, I made up this this matrix. The MBP is a 8 ounces lighter, i.e., half a pound. The display is subjective for me because I prefer matte and want the faster refresh. The MBP has higher resolution (against Razer's FHD but Razer has 4k where as apple doesn't). The MBP has a brighter display. In terms of processing power, GPU, storage, keyboard (not shown), ram and battery size Apple loses out. I will say Apple is able to squeeze out more hours out of the box then the Razer but from my research it appears fairly easy to get 10 hours out of the razer with a handful of tweaks.
While this is subjective, to me it shows the razer beating Apple in nearly every category.
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Edit: Dell wins some categories, or ties with Razer but from my research I've exluded them. They seem to have a throttling issue, so that's not something I want to deal with
Nice comparison table. I think overall for me Razer is the winner in terms of a fine laptop, it's build quality and capabilities will definitely beat the Apple and the Dell (I think Apple's build quality sometimes get overrated, it has a lot more flex than people like to admit!). Like you I also like a matte screen, I actually found my FHD matte XPS 13 9360 screen nicer to use than the rMBP 2016.
The only thing stopping me from purchasing it (other than that it is out of stock/not released in UK) is the RMA process. With Apple, and even Dell, I have a bit more confidence with up to 3 years (4 years for Dell) cover a long with the service it comes with, but with Razer I couldn't find any extended warranty in the UK - and to boot, their RMA process is nowhere near as good as Apple's/Dell's.