Choosing an HRV...My Thoughts....
1. Supplies the home with fresh dry air.
2. Removes stale air and removes excess moisture.
3. Recovers heat or heat/moisture
For a low energy home we need an HRV that is as efficient as possible. With the ventilation unit taking care of exchanging most of the air in the building, having an efficient one will pay for itself in the energy saved over it's lifetime. Zehnder HRVs are probably (http://zehnderamerica.com), some of the best HRVs on the market (available in North America) but they are way too expensive. They have some amazing features; like preheating winter air using a ground source brine loop and summer time bypass mode that completely bypasses the HRV core to bring in cool nighttime air. They also use electrically commutated variable speed motors which are super-efficient and provide more CFM per watt consumed than many standard HRVs.
Recently, several Canadian HRV manufacturers have started building more modern HRVs. The HRV design has changed very little in the past 20 years. An HRV was typically one size fits all. There was very little that could be done to change the CFM other than increase the static pressure of the ducts by installing an inefficient system or changing the depth of the duct diffusers in each room. Some new models offer the best technology seen in European HRVs. Both LifeBreath and Venmar make several models of HRV/ERV with ECM motors. This increases the efficiency of the units drastically compared to older models.
The LifeBreath 195ECM (http://www.lifebreath.com/products/residential-ventilation-hrv/195-ecm) is one of the most efficient on the market. It has an Sensible Recovery Efficiency (includes heat and the use of electricity for the motors, etc) of about 85% at 0 Celsius. The Venmar X24ERV (https://www.venmar.ca/135-air-exchangers-x24erv-ecm-new.html) has an efficiency of about 84%. The Venmar is an ERV. Opinions on the use or ERVs have changed a lot in recent years. Here is the old map: