Con:
- August is quite hot. Starting at the 5th station allows you avoid some of the heat.
- More walking
- More weight (Unless you want to be additional food/drinks in huts at relatively higher prices)
- More time required (if you have only a few days in Japan, it's probably not a great idea to walk the whole way when you can take a bus to the 5th station)

Pro:
-You can claim that you climbed as much as possible.


Personally, starting at the 5th station was enough for me. The climb is IMO relatively easy and there's not much too see. The next time I'll climb Mt. Fuji, I'll get a sleeping place at a relatively a station again. It beats staying outdoors (I had freezing rain starting around station 8.5 or 9 the night I climbed), allows you to avoid some of the masses (climbing the first part from the 5th station in the afternoon is quite nice as there are relatively few climbers) and allows you to climb the Fuji in day light (doing it in the pitch darkness is doable but less enjoyable).

It's much more busier in the early morning hour. I got into massive queues (yes. Queues) around 2 or 3 am and it took relatively long to make the last ft. in elevation.

Yoshida trail was used by roughly 60% of all Fuji climbers in 2016 as its 5th station is the highest. If you're going to do the journey from the very bottom, you might as well use one of the other trails where you won't be stuck with thousands and thousands of people.