"slow" makes no sense....in a technical sense, since the resistance is lower, the amperage would be much, much higher, thus electricity moving through the coil much faster (which is why 28 works so well on mechanical mods also)
if you're talking about heating up time, i really have no idea what you speak of, as it is nearly instant on most everything i use, and on a mech, it glows as soon as the button is pushed (at an average of 7 amps to the coil)
At more typical resistances (1.5-2.2 ohm), it's slow to heat up. Just read any of the thousands of posts here where people using it at higher resistances say it takes a while to heat up. I've even seen people recommend that you hold the button for about a second before bringing the device up to vape. I've rolled the coils and tested this myself. It vapes fine at 0.8ohm on a mechanical mod, but I definitely don't recommend it for the average person with a provari and a genesis atomizer looking to vape at 2ohms.
Make a 32ga coil at 2ohms, and make another of 28ga at 2 ohms. Try both on the same mod and tell me which heats faster. Extrapolate that to extremely heavy wire and consider which heats faster, thicker or thinner?