I would compare the hardware CPU / Memory / firmware / software running on the Vera, SmartThings2 and RPi2.
Go for the gold (faster CPU, more memory, low power, tight programming) is my personal suggestion.
CPU / Memory probably would be of a higher priority relating to what firmware / software is running.
If you are a tinkerer with hardware and software relating to multiple technologies then run with software on whatever OS that lets you do that tinkering with no stifling depending on your knowledge base / comfort level of this stuff.
You can do amazing things today with simple basic stuff with no or a very small kernel base.
Geez look at the Leviton OmniPro 2 / Elk M1 combination security and alarm panel still running fine with a CPU and memory base that is some 15 years old these days.
You can now too integrate the ModMyPi PIco uninterruptible Power Supply & I2C Control HAT to the RPi2 providing 8 hours of back up running stuff. While it will chat fine with those wireless Z-Wave trinkets it will not provide 120AC power for your Z-Wave connected lighting (well nor any 120VAC lighting) and keep it running even if the internet is down.
Here have the Rasberry Pi 2 running Homeseer 3 lite (Zee-2) with an integrated GPIO Z-Wave Plus and PiFace RTC shim and 1-wire network to provide a bit more resilience to the OS and hardware. (note too I have added a serial UPB and X10 and WIreless and Davis Vantage Pro 2 weather console automation widget with no real issues to the RPi2)
Note too that the specifications of the current RPi2 are: (posted a similar message on the Homeseer forum this morning and it was removed for whatever reason - hate when that happens - and does make me upset relating to a bit of over moderation). IE: this information is public knowledge relating to the RPi2 and yes the Homeseer 3 Zee-2 and Z-Net device run their stuff on an RPi2. It is not a secret and HS just put their label on a custom RPi2 case. Homeseer was the first automation company to do this and I did purchase the original Zee running on a Linux OS mostly because Homeseer ran on Linux and it did work on any Linux box I had as I tested it right away. Homeseer is not free for public consumption and you do have to pay for a license to run it on whatever.
- A 900MHz quad-core ARM Cortex-A7 CPU
- 1GB RAM
- fast GPU
- great little KODI box
That is pretty fast (relatively writing).
You can do similar with the free Home Genie automation software running on the RPi2.
The Homeseer 3 interface GUI is plug n play and easy button stuff running using Mono on Linux.
Note pushing the RPi2 to CCTV or NAS or as a Media server while concurrently doing automation is not recommended; but best to see for yourself.