The definitive OTP ( Off-The-Peg ) List (<£500 and <£1,000 sections)

Have a look here: https://www.lfgss.com/thread9085.html

Re quills:

The advantage of a quill stem is that you can raise it up and down without needing to adjust the headset.

The disadvantages (on the whole) are:

• heavier
  
• less stiff
  
• less secure compared to say a 4 bolt system (but probably more secure from a security POV)
  
• lack of front loading ability (usually) so swapping bars is harder
  
• usually 1" and therefore limit modern fork choices and upgrades, as well as being less stiff
  
• no oversized (31.8mm) option therefore limiting any bar choices - pretty much all style of bars come in a OS variant.
  
  

... I think that's most of them.

Oh yeah and cost. Nice quality quill stems are generally IME expensive whereas you seem to be able to get decent last season type aheads at a discount. Equally you can get cheap ones that seem to function better than cheap quills. I'm sure someone will disagree with this though.