The only con I can think of with stacking laundry pair is that I'm not tall enough to reach the controls when my pair is stacked.

Stacked laundry allows room for a sink where it wouldn't be possible if they were placed side by side.

@Mr Ironwood -- Good to know, I wish mine did, I would have definitely stacked them.

I prefer a top loader washing machine which means that even though it is possible to invert a dryer and stack over the top, it is still just a little bit too tall for me to reach into. Which means my clothes dryer lives in the garage, and the washer is at the other end of the house, in the laundry. :(

I prefer side by side and top load, I have an HE washer top load its great in case something is forgotten it can be opened and in it goes. Front loads you cannot open them .
http://www.sears.ca/product/maytag-maytag-bravos-xl8482-53-cuft-top-load-washer-white-mvwb750yw/626-000285270-PAVT144AWW

My daughter-in-law and sister have front loading washers and complain about an odor with them.

If you have a front loading washer, you need to leave the door partly open all the time. We dry the water out from the seal after we are done using it and we run a cup of bleach through it once a month on the cleaning cycle to keep the odors away.

My top load washer smells bad if the lid is left closed. It's all about maintenance with either.