I am at this same dilemma of selecting between these units, and trying to keep myself from toying with an Arduino to create my own...
For me, the stoker is much better thought out, and as an embedded appliance it's setup way better with the internal httpd server, external ethernet port, etc...on top it offers multiple units to be controlled through one unit, and is much more expandable. I probably don't need that, but I do have several different 'ques it could work for.
I tried to call Fred about the Guru, but with a couple calls and then left a message, but it wasn't returned. Not the emails I sent to them either.
John is located on the other side of the bridge from where I work, and answered the phone when I called him the first time. Nice guy, and local for me which is a slight plus,,,and he'll let me come over to his shop and get a demo and/or save postage.
On the guru side, it has been around longer and seems to be bullet proof, so to speak...
I have a friend that uses one and touts how easy it is to set and leave cooking. The stoker seems similar with some connecting the dots to get everything setup.
Having worked in the embedded space, I am inclined to go the stoker route, but if someone was wanting to sell a guru cheap to get upgraded to a stoker with more expansion, I would entertain that also.
Amir, doesn't your software only run on Windows? Unfortunate for me it is the one platform I can't stand to run. In talking to John I would only need to send http requests to the server, so that is workable for me if I wanted to write my own, in fact I have a library in open source that works on UNIX and Linux which sends http requests to a server, so that could easily be scripted...there's a several program that do the same as well (wget or curl come to mind). That is certainly an attraction on the stoker, anyone can write code and get the info through http requests, and it leaves a much more open platform to nurture the smoker community at large. I don't know if that is an advantage or not, to some it will be a deterrent...and it's easier to go the simpler "push a couple buttons" that the guru offers and be happier in the long run...but the open development model will allow folks to share their programs, as you have done...kudos!
The other thing is that with about $10 worth of parts, and a couple probes, you could probably do the same thing with the Arduino. But time is money as they say...