IMO you are argueing about positions between nowadays no clear distinction can be made.
Just take Zambro he can play either winger, wing mid, or wingback.
Of course the heart of the thing is the balance between defending and attacking, but its very rare to find an original side-back in elite clubs, cause its a kinda waste.
No matter how we call it, but in 433 you need guys on the sides who can do both defend and attack in a decent level, if more attacking, you need better defending mids and vice versa.
btw our lineup with Davids was something like 433 not a strick one, and as you can see on the right: a good def who likes to attack is companied with an attacking minded Camoranesi. On the left there are Zambro a good attacker who like to defend partnered by Edgar a good defending mid, who likes to attack.