I own Rolex and Grand Seiko.  Most people agree GS have great craftsmanship.  I have found GS has spent a lot of effort in the design and in the details.  Max is right about the clasp of a GS.  It can get annoying.  If I really have to compare the two brands, the GS has too many watches with a similar design.  The height of most of their watches is too high.  The power reserve is a neat feature but not to everyone's liking.  The 20 Bar is misleading, you cannot go scuba diving with it unless you wear the diving GS. For GS to be more successful, they should fix their so called "Sports" collection. 

Put it simply, is GS a tool watch, a rugged watch like Rolex?  I guess a majority of people do not think so.

Do collectors see unique features that have been improved over generations of the same product line?  If there are I must have missed them.  GS bring back some vintage models but there is no evolution.  Rolex is good at continuously improving an already good product because most product lines are an icon, built for specific purposes.

We should stop comparing the two brands.  GS unlike Rolex do not spend millions on sponsoring sports events.  They worry about their sales figures therefore they launch similar models  frequently in a year.  They know their niche areas.  They want to be "Rolex" but the two are taking a different path.

For watch collectors, they are happy wearing a GS.  Because they already own many different brands.  For some people, owning a Rolex is the first goal in the watch collecting journey.