Amazing 300 introduces a mediocre villain, who is later changed into an anti-hero, but still sells the symbiote in an auction to gangs, and gives the money for charity.
And Michillinie wrote MJ as a sex doll moreso than other writers did.
And I still don't like McFarlane's pencil work, or him making the "spaghetti webbing" (said the back then E.I.C. Tom Defalco), extra large lenses, and too many lines in the suit. It's nice that he reverted Spider-Man back to the red and blue, but his revamp of the suit is not my thing.
At least it was less eccentric than the way he did it in the no adjective title.
On the other hand, Amazing 400 ends with a stupid cliffhanger, ties in to the nonsensical overstretched and revisited Clone Saga, the emotional death scene is retconned to "that was an actress".
MJ was pregnant, but that was gone, her baby died, then a retcon ignored the little Spider-Girl.
Bagley's art is great, but it's not enough to save the story from future messes.
In that aspect, Amazing Spider-Man 300 wins for me.
Not taking following mistakes into consideration and taking the stories as their own thing, I prefer the art in Amazing 400, but the story in 300 is more fun, despite the stupidity of Venom's origin story.
Again, another vote for Amazing 300.
AMAZING SPIDER-MAN 300 is my choice.