chromecast is the easiest / fastest setup as long as you have a tablet thats always around to use as a remote
plex app streams your local media for free now (well $5 for the app but no monthly fee) so chromecast now does pretty much everything you could need.
I used xbmc before. honestly it handles local media better, but the initial setup and customization is a bit of a pain and it can't do netflix/hulu/youtube very well. (there are ways to get it to work acceptably but they take time and still aren't as good as chromecast).
If you mostly watch streaming online stuff and just want to plug something in and have it work right away then go with chromecast+tablet. if you mostly play local media and are willing to take the time to customize everything, it can look cooler with xbmc.