Here is a possible con against bottom-freezers:
I had a Daewoo somethingorother (forget the model) fridge with the freezer on the bottom. Please note that I am not an engineer but this is my understanding of how it works and so why it went wrong.
Self defrosting fridges like mine have a drain, so any condensation or moisture goes down this special drain and drips into a tray above the motor, where the heat from the motor helps it evaporate.
Because the freezer was on the bottom, the drain ran down the back of the fridge (upper) and then into the freezer (bottom) on its way to the tray. Slowly, over the course of the six years I owned it, a little bit of the condensation in there froze before making it out. A little here, a little there, slowly adding up until every day there was a puddle of water under the fridge. Mop it up, a few hours later it was back. I took the freezer drawers out and saw ice, I removed the back cover and saw more ice. The drain tube had blocked up with ice, so then any water landing on top stayed there and froze producing more ice and eventually filled the cavity there until the water had nowhere to go but out and onto the floor.
I spent the afternoon chipping away and pulling out blocks of ice with the aid of a hairdryer before I got far enough in that I could tip a measuring jug full of boiling water into the drain, melting down through the plug of ice and clearing it. That fixed the leak, and I pulled several margaritas' worth of ice out in the process.
So there you go.