My Venue 8 Pro is a 5000 series (5380) that comes installed with Windows 8.1. I purchased the 32GB version.
The thinking behind the 32GB instead of the 64GB model was that expansion is possible with insertion of a microSD card. The 32GB was 55% the price of the 64GB version, and probably a fair differential in costs. Time will tell, because time is money.
To increase the storage, I purchased a 64GB SanDisk microSDXC UHS-I card with adapter (SDSDQUP-064G-AW46A).
I recorded some steps I performed in an attempt to get Windows 8 to be a productive platform on this device here.
I installed Windows 10 buy upgrading rather than a clean install. This left all the Dell programs intact. Subsequently, I uninstalled the Dell programs. They seemed to fight with Windows 10 for program and driver updates.
Windows 10 seems snappy and more stable. However, There is not enough room to upgrade to Windows 10 Home, version 1511, 10586. I further uninstalled all the programs I installed previously, have run the disk cleanup in settings, and even a uninstalled few Microsoft programs. Still there is only a paltry 4.5 GB free space giving the impression that more files need to be jettisoned.
This is a false impression and there is a way forward. It is just very unclear and Windows does a poor job of helping the user. If the system is rebooted and the disk cleanup run again, and again, yes repeatedly, the old system files that are archived will eventually be deleted. Still not enough space is freed to run the upgrade. I believe this is due to the insistence of the upgrade processes to save the older system files. Their seems to be no way around this. Eventually, at failure to update a system note pops up and asked to identify the problem. After a long delay it reports that not enough room is available and desired 10 GB of space, there was only 7 GB.
It did suggest that another disk be connected. Curiously it could not see the 64GB microSDXC installed and mounted already. It did eventually have a button to attach a drive, presumably to save the system backup files to since once attached it warned that the disk should be stored in a safe place. Curious that all this presumes that a user expects this to happen without documentation. Attaching the microSDXC at this stage did allow the upgrade to proceed.
This upgrade process apparently takes many hours as it has been at it for over three hours already and is only 4% along. Since the Venue 8 Pro only has one port for power and USB 2 I have to use the microSDXC since I do not have an adapter that allows both power and a USB drive to be plugged in at the same time and I certainly do not want the upgrade to fail due to battery power running out.