Ahead or Quill for new build?

dont understand what you're saying here, gizmond.

so much easier changing an ahead stem. also, you can flip it up if you want a more comfortable ride. you'd need a whole new stem if you want a diff angle.

and if you're changing bars (eg track to mtb risers), with ahead's removeable front mount, you can do that in a minute. would take ages if you're on quill and you have bars with grip/bar tape

Dis-agree, it much quicker and easier to change a quill stem than ahead. about 30 second I would say; undo bolt, lift out bar stem combo, drop in new bar stem combo, straighten, tighten bolt. Takes me longer than that to get the 4 bolt on the ahead undone.
I always keep bars and stems combo together, 90mm stem with risers, 110mm stem with drops.

Everytime you do anything with your ahead stem, you have to re adjust your headset bearing load, which is crazy.

That said, after the winter when my bike becomes 'all about the track' it will very probably be rocking ahead.