If you gave me the Note 2, 3 and the iPhone 6+ I guarantee you I could tell the difference.
I even felt the difference on the Note 2 and 3. While the Note 3 had like a 1mm smaller width its edges weren't rounded as Note 2 so the Note 2 felt smaller and more ergonomic to hold, for an example. The rounded edges of the iPhone 6+ will be the same compared to the Note 3 and 4.
Lets rephrase that, if given solid aluminum blocks each with the note 4 and ip6+ dimensions I'll bet you wouldn't be able to tell the difference.