Wider is definitely better than deeper. Cannabis produces a shallow but wide root system, especially when growing clones. A 30 gal trash can will be able to grow bigger and better plants than a 5 gal bucket - 5 gal is much, much to small for outdoor.
The minimum size you should go with for outdoor is 25 gallons if you want to make it worth your while. However I am pretty certain that a 25 gallon
smart pot or plastic pot is going to be cheaper than a trash can. The rubbermaid containers would probably work well too since they are nice and wide.
Don't plant directly into native dirt either - 99% of native soil is crap. A raised container like a
smart pot or rubbermaid bin (or better yet wooden raised beds) will give you better aeration, better drainage, and better control over the conditions of the plants roots. Cannabis likes light, well aerated soil with good drainage, and lots of organic matter so keep that in mind.