The potting media will determine pot size :-) With a fast draining, not excessively water retentive potting mix, a larger container size is immaterial. I use the 5-1-1 soil mix 90% of the time for all my containers and typically upsize to whatever I feel will be the best fit for long term growth without a need for frequent repotting or root pruning.

thanks @gardengal. this pennington moisture control mix is 2-1- 2.4 (if i did my math corectly)

I'm not familiar with that product but doubt that would be my first choice - I find moisture control additives to be problematic. And I believe those percentages relate to fertilizers that may be included rather than the actual potting mix ingredients.

If you are not familiar with it, the 5-1-1 mix is 5 parts composted bark fines to one part peat and one part perlite. And that would be what I would go with if I wanted to pot up to a larger sized container.

i thought your 5-1-1 meant NPK. i will look for the mixture you suggested.

update: I potted up the 2 arbs today directly in the smallest (20") planter. The O. Fragrans and Yuletide I'll lilkely put in 5 gallon pots, then sit the pot in the 22" planters.

If you intend to move the containers around, that is likely to be the real limiting factor. I have a 30 year old bay tree in a 22 inch pot. That is the largest that I can move into the house in the fall, so that is the largest pot it will ever get.