The Suns fans are in a fair consensus over at the Bright Side of the Sun that Isaac is the best player for them at #4 and their GM would take that type of player. Isaac is much longer than Ariza. I don't see the comparison.
I also think Donovan Mitchell (who I just started a new thread on) is a better prospect than Dennis Smith Jr. Check him out and tell me what you think.
EDIT: And in this draft which is being declared the best since 2003 in the Top 10, you go for two stars at #5 and #10. Why aim low for "a complementary piece"? I think perhaps you just got an attachment for Smith because he has an impressive vertical. But I am telling you I strongly believe that you and others are overrating him and this will be played out soon enough. If you watch Donovan you will see he has similar aggressiveness as an offensive player who can drive into seams and make plays in traffic. But he's more potent defender who can defend three positions.
He has the physicality and the attitude. He would probably lock down Smith with ease.