Neither, if they're being bought before a Har/Quick or Har/Smart. The casting speed boost is different from the AT/MF casting speed boost, meaning they'll both benefit you.

Get one of the two. Har/Quick is cheaper. Har/Smart makes Ra-techs simpler to use, in my opinion (as it only shortens their "range before they go boom", not the radius of the "boom" itself). It also shortens range on simple techs (Foie/Barta/Zonde/Diga/Megid). It does not affect range on anything other than Ra-techs and Simple techs.

Har/Quick doesn't give a range decrease, but comes with -100 TP. The casting speed it adds makes up that TP reduction and then some.

After you get one of the two (or if you already have one of the two), then get a Lumira/Spread, as the extra range is sometimes useful. Hizeri/Concentrate is bad, bad, bad. Please don't waste money or time hunting it.