It’s entirely down to personal preference. The pollen blocking properties of each one are exactly the same.
Otherwise, people choose according to the smell they like best and/or the commonly accepted properties of the variety.
Keep one by the bed, one in the car, one in the office, and one in your pocket or handbag.
HayMax Pure™ contains no essential oils. It’s perfect for those who don’t like the smell of Lavender or Frankincense, or who are particularly sensitive.
Aloe Vera has no added fragrance and can soothe that sore nose at the same time as it blocks the pollen.
There are many books about aromatherapy oils that can give you more information –The Encyclopaedia of Essential Oils by Julia Lawless has been recommended to us.