This NUC can easily handle both those, and Windows 7/8(.1). I guess it breaks down to what you've packed it with (RAM, internal storage, booting from USB etc), and what, if anything, else you'll be using the NUC for except XBMC. OpenELEC is "nearly" Plug'n'Play - you can install and boot it off a USB stick if you want to try it out before settling on something. Its also clearly quite resource-efficient. (Note: performance on some areas, when running of a usb stick, may clearly differ from running OS off e.g. an internal SSD)
Personally I use Win8.1 pro in my DN2820 NUC, but then again I use it for a lot more than just XBMC, including some win-only apps - and wanted the "Full HD+5.1" Netflix package (Which is currently only available through this app, if you want a "Netflix interface". UPnP through PlayOn is a possible workaround, but HD is not working with XBMCbuntu atm (thread
here).
There has been some issues with PAP (Protected Audio Path) with the NUCs under Win8. Unless it has been resolved very recently, that means DTS-HD bitstreaming is a no-go on Windows. Works fine on OpenELEC though, and I would expect the same with XBMCbuntu.
There is a very detailed and extensive thread on this NUC, issues, fixes, updates etc - covering mostly OpenELEC, Windows 7/8(.1) and XBMCbuntu - here on this forum. The likelyhood of any question or issue regding this NUC, to be covered there - is quite strong.
So PLEASE use the search function.
Intel NUC - HTPC (Bay Trail 2013 edition - DN2820FYKH)
TIP: Do update (As of this post: Bios version 34) and get aquainted with the UEFI/BIOS first, so you understand what options does and affects what (else). Quite a lot of the common issues have been down to improper UEFI/Legacy BIOS settings.
