A bit over a decade ago the 'rat rod' movement was started in the hot rod community and it as been the scourge of the traditionalists ever since.

Above is a beautifully built, traditional hot rod.  It was built by Vern Tardel for Ryan Cochran of the HAMB - both of which have literally written books on how to build a traditional hot rod.  What makes this car really work well is the the perception of its balance, grouping, and use of positive and negative space.  From the 3/4 view it is easy to see that the vertical line is consistent from the front to back and all of the lines line up parallel.  It starts with the back of the grill shell lining up with the cowl, A and B pillars, and even the seems of the doors.  This consistent grouping allows the car to be seen in its entirety instead of your eyes focusing on one aspect in particular.  The headers hang below the car and leave a gap between them and the ground that is equal to the height of the windows between the chopped top and the belt line.  This allows for a sense of horizontal balance.  Finally, the use of contrasting colors between matte black and chrome allows the car to be broken up a bit and not too boring while still maintaining a central idea and theme.

The car above is considered to be a 'rat rod'.  While they have gained a large following, usually with amateur and budget-oriented builders, most professionals have a deep seated loathing for them.  For starters, the complete lack of balance and grouping causes an undue about of stress to the viewer.  No two parts of the car have any common lines to tie them together.  The body and grill both have curves, but the curves have completely different radiuses and are mounted at different angles.  While there are no flat panels anywhere on the car, the frame juts out from an arbitrary point on the front of the body and runs totally flat to the front of the car.  The frame is a rectangle framed by the curved firewall, curved grill shell, and rounded headlights.  Furthermore, it does not even line up parallel with the ground.  The car is also disproportionately balanced towards the front, giving is a sluggish and offset look.  This is the result of jamming as much as possible into the engine compartment and leaving nothing behind the car except for the tires and axle.