Originally Posted by kwadric
Maybe a computer engineer or computer scientist will chime in. I don't want to regurgitate what I read incorrectly.
I highly doubt you'll run into programming memory space issues on the 'Duino with a project like this (unless you want ethernet)
Pro - Real-time operation, many analog-to-digital pins with reasonable accuracy (8-bit, I think?), extensive documentation (good for someone new to this area!)
Cons - Limited UI options (think push buttons/LEDs/small LCD/seven-segment displays), limited internet connectivity (RAM/PROG space limitations). Also the ethernet shield isn't cheap. Stuck with C/Wiring for language (might not be a con depending on your experience)
Pro - Internet is easy (including WiFi!), full linux on the board means full TCPIP tools, GUI, video out, etc. Cheap (actually cheaper than Arduino + Ethernet shield!). Many choices of programming languages (yay, Python!)
Con - No Analog-to-Digital (but you can add cheaply with these http://www.digikey.com/product-detail/en/MCP3008-I%2FP/MCP3008-I%2FP-ND/319422
, a breakout board like this http://www.adafruit.com/products/914
and some soldering), linux experience def needed to leverage full power. NOT guaranteed real-time execution (though it might not matter too much in this case).
I'd say weighing the above: Go arduino if you DON'T want internet connectivity and can live with the GUI limitations. If you want to control/administer/view the thing over the web, go RPi, just keep in mind you will need an external A2D converter circuit.
To expand on the real-time issues: These really only come into play if you're looking to switch something off and on with millisecond accuracy (say to keep an LED at half-brightness, or other PWM tasks)- that would be difficult to do with the RPi out of the box. If on the other hand you only want to turn a fridge on/off every few minutes to keep a constant temperature (for exampe), you'll have no problems with the RPi. Feel free to PM me with any questions along the way, I've got a few years experience in this area.