I dunno what it is, but I genuinely dislike the straight pylons, when applied to the "Discoprise".
They look fine on the TOS Enterprise, but there's something about the look they give the modernized version that I just don't like.
I much prefer the swept back pylons. Makes it look sleek and fast and somehow more modern while still being gloriously retro. Plus, it goes well with the NX-01, which is always a plus in my book.
Opinions will vary.
*credit to Marc Bell from Artstation for the image of the straight pylon version.