The nice thing about the Raspberry PI is you can easily grab an SD card, load up NOOB boot loader with a number of different OS’s and you are good to go.
I tried RASPBMC and OPENELEC. My experience is that OPENELEC was more responsive.
After loading it up, I liked the idea that I could use an old android cell phone I had laying around as a remote. This works in both RASPBMC and OPENELEC.
Also, let me give a laymans view. OPENELEC provides the same Media Center views and options as RASPBMC, but seems to have a difference in the underlying workings. So anything you can do with RASPBMC you can do with OPENELEC.
The scope and depth of channels available was very impressive. The ability to stream music (like from SKY.FM). It might be a little slow in some of the transitions, but so long as it has an ethernet connection, it streamed pretty well.
My absolute favorite part of the OpenElec on the Raspberry Pi is the simple ability for it to access all the media on my NAS where I have a LOT of movies, series, tv shows and music. They streamed up to 720P quality with no hiccups. I didn’t have to deal with special codecs or software loading. It worked.
And OpenElec includes “scrapers” which performs a data gather with thumbnails against your files. If you look at info on a file it will provide you with the thumbnail and a quick write up on what the file is about.
Of course, the functionality goes far beyond streaming NAS files. If you have time, searching against XBMC for the plethora of channels you can stream, whether internet content or normal broadcast content.
I really can’t go on enough about it. The OpenELEC distribution is pretty solid within the limitations of the hardware.