Holiday avocado tree pollinator
They are both A flowering type so not ideal as pollenizers.
Pollenizers are more important for commercial growers, presuming you are a home gardener.
It is more important that you have lots of bees visiting the flowers. Avocados have a long flowering period and the flowering opening is not perfectly timed so there is potential for close-pollination without the pollenizer.
Perhaps it would be best to describe your situation and your aims for the avocados.
I have seen web sites that sell the “Little Cado” and list it as either ”Type A or B”, or as “Type A/B”. I have also seen references to the weather climates in colder parts of California and that the A-B flowering cycle is disrupted which can cause both the A and B flowers to bloom at the same time. Because of this information, I was just wondering if I could plant the “Little Cado” as a pollinator for the Holiday, or the Gwen, here in Sequim, Washington, where the climate is colder than California. I have limited space, so I want to plant dwarf varieties of avocado trees. I am going to put up deer fencing and provide weather protection for the trees in the winter. I was thinking of planting a Bacon avocado as a pollinator and keeping it well trimmed, but this is another tree in limited space and I do not know how well the Bacon would take to the trimming. My goal is to simply have a small orchard with fruiting trees that does not interfere with my current view of a large irrigation pond and of the mountains. I am thinking of planting a dwarf Peach, Nectarine, Apricot, and Avocado trees. The pollination of the dwarf Avocado trees is my issue that I am trying to resolve.
I trust the University of California's avocado database, and Wertz is listed as an A-type (http://ucavo.ucr.edu/AvocadoVarieties/VarietyFrame.html#Anchor-47857).
For weather data I use WSU's AgWeathernet (weather.wsu.edu). Sequim is definitely marginal for avocados but with frost protection, a hobby orchard should be fine.
Wertz's and Holiday's weeping habit would be good to protect the tree in the winter. Gwen is a good option, as is its "daughter" Gem, it is a semi-dwarfing, slow growing tree which is fairly frost tolerant.
You are correct about the flowering patterns being affected by the weather. New Zealand would be the closest analog to Western Washington, and the flowering pattern there is significantly affected by the weather.
You might get less fruit without the pollenizer so if you have the space, plant two cultivars. If not, plant your favorite. If you are able, try grafting the pollenizer onto the main tree. If you are looking for a good nursery, Persea Tree Nursery in Fallbrook, CA is recommended.
Getting bees to visit avocado trees if the other fruit trees are flowering will be an issue. Avocados are bees' least favorite tree.
Further reading on the topic at http://ucavo.ucr.edu/Flowering/FloweringBasics.html
In summary, for a hobby orchard , keeping the trees alive and getting bees to visit the avocado trees is more of an issue than the pollenizer.
All the best, would love to know how the trees do.