Raven is correct. Vazkii believes that neither of them require enough mana during "standard" use to require the throughput of sparks. You can GREATLY speed up the process by understanding the rules of mana bursts though. Travel time is the single biggest bottleneck with mana transfer via burst. ONLY one burst from a spreader is allowed to exist at once. This means a two block gap is nearly twice as slow as a one block gap (assuming your mana spreader stays fully saturated with mana). A no-block gap is also significantly faster than a one block gap (not instant, the spreaders have a slight internal cooldown, but still WAY faster).
Lenses are also very helpful. With a touching system, I'm not sure if velocity is a good idea (haven't done any testing), but I know flat-out that potency is. Obviously so is upgrading your spreader to elven and then gaia.
i know that sparks arent necessary, an elven mana spreader with a potency lens next to the brewery completes the potion in less than a second.
i just think sparks look cool, so i wanted to use them if possible.