HRV - very good system but sales methods are appalling, pushy and money driven and now run by Australians. DVS has too few vents but are changing but getting expensive as a result. Healthaire - very good system but controller lets them down. AMS - useless controller, always failing. Weiss - average. SAYR - very good but new to market, they use the HRV motor. SmartVent cheap equipment and noisy, should only be used for a bach. Ecoair - cheap and nasty. Uses an off/on switch. Avoid them. Driveair - shudder. MoistureMaster - they needs heaters in the roof to work (their salespitch). Cleanaire - Not a PPV but a true Heat Recovery Ventilation but needs a totally 100% sealed house to work properly and overseas websites back this up. .... The rest (5-6) aren't worth even looking at except for baches.
Plenty of companies to choose from but the most important thing to look for is high flow, vents everywhere and excellent control system.
Hope that helps anyone