Honestly I wish I could have the best of both worlds (for me) and get a MacBook with 32 GB of RAM, a 3 TB hard drive, and the latest, greatest Intel chipset that would rival any other serious development machine for under $4k.
I Need the MacBook to do the following stuff: Video editing (with Final Cut X) Generic Programming (C#, Swift, HTML ). Video editing will always benefit from more processing power. It's the most demanding task in your list by far.
A toaster would have sufficient processing power for these tasks. Your choice won't really impact them. If you just wanted to focus on mobile game development then the Intel GPU would be fine but if you want to get into game development for more demanding platforms like standalone (Windows, macOS, Linux) or the consoles then you will almost assuredly need the dedicated Radeon GPU. A toaster is fine here too. The only real reasons to use a Mac for game development are: A) You are developing for iPad or iPhone B) You have a strong preference for Final Cut Pro, even, though equally as good options exist on a PC While number two falls into the subjective category about as much as any other subjective reason to go for a Mac, I think option A is really the only solid reason to ever buy a Mac over a PC.
Objectively, Macs are notably less power than an equally powered PC. It is not uncommon to find an equally powered PC for 1/4th the price. While that PC/laptop probably won't look as pretty, or feel as solid, it will have all the power you need, and arguably better support. Support from Apple has (subjectively) really gotten pretty bad - something that made their higher premiums often worth it in years past.
Not that I am trying to throw in a wedge here and make this a Mac vs PC debate, but I feel like it has to be said when you are looking for something to develop games off of. If you are not making apps for iPhone and iOS, there really is no reason. Especially if you want to develop for the desktop.
Otherwise, most any Macbook Pro should be able to handle the Unity Editor and most games at enough of a level to develop off of them. The one thing that I prefer on a Mac to Windows is the bash/shell. But Mac is built off of Unix.
The shell is extremely similar on a Unix-based OS, so if I am trying to get the benefit of easier shell scripting, I am personally just going to set up my windows machine with a second Unix-based OS.