i have the hydor ATO and for the money i wouldn't complain about it. the only thing you have to watch for is the outlet plug that you will be plugging your pump into. i have a Aqualifter and i had to clip a portion of the plug so that it will fit into the ATO, nothing you can't do though.
for the other ATO you are thinking, you would need a pristine glass so that the sensor can detect the water level. any smear or dried up water marks will interfere with the reading and making it unworkable. i do like the compact design and how it has its own pump.
you just have to weigh out the pros and the cons.