For my purposes the Pi-2 is an exponential improvement over the B+. I've been using the Pi for thin clients, video servers and the like for a number of years. I don't do robotics or anything like that, so I can't talk about it. The Pi-2 can now work very well as a thin client and smoothly play YouTube videos and video files with omxplayer. Chrome doesn't work properly, but Iceweasel (Mostly Firefox) does. Epiphany browser is installed but Iceweasel browser works better for me. I've also used Pi-2 to run a proxy and socat to telnet to old serial ports on an old Unix machine. Running 3 simultaneous connections is no problem. The addition of a quad core processor is a huge improvement for me. I'm using a 16GB Micro SD Raspian image. I had trouble with NOOBS. The best SD I've found is the pny turbo. They are relatively cheap and 90 MB/s. I have used both Banana Pi and Radxa and the Pi-2 outperforms the Banana Pi and is almost equal to the Radxa Pro. The only hand-based microcontroller I've used that is significantly more powerful is the Odroid xu3 lite, but that's not a fair comparison as it has 8 cores and 2GB of RAM. It's also over $100 and uses more power. I also found the Pi-2 to run noticeably cooler than the B+. I have a couple of B+ cases with fans that match the Pi-2, but the fan isn't really needed and is quite noisy. Also, heatsinks are probably overkill, but certainly adequate. My guess is that they run cooler because the memory is no longer stuck on the social so it can cool better.
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