Here's my .02; If you want the ability to monitor/control your WSM via your home network, graph your cooks, receive email updates of your cook status (pit and food), control more than one cooker at one time etc. than Stoker's your device. However, if you're just looking for a set it and forget it Automatic Draft Control Unit without all the bells and whistles of Stokerlog than the Digi is probably the way to go.
I'm basing this on being a Stoker owner and my good friend Ed C. being a DigiQ owner. We both bought ours at the same time and have been at cooks where each unit has been used. As a DigiQ owner I think Ed would probably agree with what I've written.
If you have any questions regarding the Stoker feel free to let me know.
And as Mike wrote, you really cannot go wrong with either unit, it comes down to how you want to use it.