The Difference Between MHL Cable and SlimPort

It's easy to take for granted how conveniently plug-and-play so many of our devices are, these days. And millions of Android phones, which almost universally charge off of micro USB ports, can output video over MHL Cable, or Mobile High Definition Link.
But MHL isn't the only video standard that can output via a microUSB port; in 2012, Google introduced the Nexus 4 and the Nexus 7 with a competing standard called Slimport. The two are essentially competing to be the most convenient. MHL has an install base of millions, and outputs to the ubiquitous HDMI standard. But SlimPort offers something just a bit different: DisplayPort compatibility, which means it can easily output to a variety of video standards.
The MHL consortium announced a 3.0 spec on Tuesday, upping Mobile High Link's resolution support from 1080p up to 4K at 30 frames per second. Future Android phones and other devices that support the new spec will be able to push video at 3840x2160 while drawing up to 10 watts of charging power; they'll also support 7.1 surround sound audio and the HDCP 2.2 content protection standard. Of course, the 3.0 spec is mostly futureproofing, since 4K TVs are just beginning to show up in stores and homes.
MHL has found its way into more than 200 products at this point, with millions of devices on the market. SlimPort, by comparison, is available in only a few: Google's Nexus 4 and Nexus 7, the LG Optimus G Pro, a Fujitsu Windows 8 tablet and the ASUS PadFone Infinity. Last year Anandtech did a good job of summarizing what makes SlimPort different from MHL:
SlimPort's support for the DisplayPort standard--specifically Mobility DisplayPort--means it can output video at the same 4K resolution as MHL, though not via HDMI (yet, anyway). And here SlimPort hasn't really made good on its potential, yet; though it's based on the flexible DisplayPort standard, the only SlimPort adapters currently available are for VGA and HDMI connectors. The upshot is that you won't be plugging a Nexus 7 into a 1440p DisplayPort computer monitor anytime soon.
Since DisplayPort can pass along an HDMI signal, SlimPort more or less works like MHL right now. Both output from a phone's micro USB port and plug into a TV's HDMI Cable port. Both will support 1080p60 video. as the MHL 3.0 spec comes into play, the two may begin to diverge more noticeably--it'll especially be interesting to see if any more Android devices follow Google's lead in backing the SlimPort standard.