Currently I use
Goodman and
Trane heating and cooling products and
Rheem Hot water tanks as well.
Your biggest difference between these products is their efficiency. In most cases, the higher the efficiency, the more the product will cost.
Currently you can get a furnace that is between 92% - 97% efficiency rating. What that means is for every dollar of gas you are using for your furnace, you will be using 92-97 cents of that dollar on heating your house, the remaining goes out your flue/vent. Most homes built before 2005 in Calgary have anywhere between 60-80% Mid efficient furnace.
Air conditioners are a little bit different. Efficiency rating is based on the amount of power it uses. The higher the SEER( Seasonal Energy Efficiency Ratio) Rating, the more efficiently the air conditioner operates and the more it costs. Right now you can get between 13-18 SEER. Because Calgary's summers are much shorter, it would take a much longer time to get your money back in efficiency by purchasing a 18 SEER compared to a 13 SEER. I usually recommend a lower SEER rating, but there are always certain circumstances were a more efficient unit is the right choice.
As for hot water tanks, same idea as a furnace. Right now you can get between 70%-95%. 70% being your typical water heater connected to your chimney. 80% would be a water heater vented with plastic pipe and 90-95% would be your tankless water heaters, also vented with plastic pipe.