Is a Gb on xbox one different?

No, it's not different. You do get 512GB, but the 478GB available is because of what is already installed on the Xbox (Dashboard, and pre-installed apps)

to put it simply

since the dawn of time

Manufacturers of the drives work out size as 1000MB (Megabytes) per GB (Gigabyte)

Software size is worked out as 1024MB per GB

due to formatting of the drive, then minus any cache/system files etc.

It's confusing cos manufacturers and operating systems typically use "GB" to refer to both Gigabytes (GB) and Gibibytes (GiB).

1GB = 1,000,000,000 bytes

1GiB = 1,073,741,824 bytes

The manufacturer of your SSD is using Gigabytes to measure its capacity, but the Xbox measures it in Gibibytes, hence the difference of around 7%.

In the case of external drives, you have the full capacity to use for installing games/apps/DLC, however, in some cases - e.g. if you were using the SSD as a replacement for the internal drive - then the Xbox would split it into multiple partitions, so some space would be taken up by the OS, some by a partition used for updates/caching etc. and you'd end up with considerably less than 478GB free.

So, yeah, in your case it's just cos of the difference between the ways the capacity is measured, GB vs. GiB.

[quote user="CND AAA Beef"]

I got my 4GB last Boxing Week for $130, and I managed to get a 250 GB HD marked down too. Overall, I saved over $50 compared to a 250GB console. You just have to know where to look.

[/quote]

I had similar luck. I purchased a 4GB at Amazon and received a $50 gift card. Applied that to a 250 gb hdd which was marked down to $87. I ended up with $237 in it.

Besides the HDD? There is no differance at all. Both 360's are the same hardware-wise, it's just one includes the HDD and the other doesn't.... because it's the irrelivant arcade model. And since the HDD is vital to the 360 funtion, getting a HDD-less system
is a waste of money IMO. So if anyone is still confused, always buy the model with the HDD.