Either will reach 27-30 mph, at 48v ( 16s lifepo4) depending on the winding speed you select.
The fastest one on the dd motor will hit 27 mph, with a 25 amps controller. A "25 A" controller means the controller will limit continuous amps to that level. But ratings are not gospel, typical 20 A controllers actually are often 22 amps.
It's important to match your controller to the battery. For example, a 15 ah ping battery should not be used with a 30 amps controller, unless the rider is very careful. Better to limit to 20-25 Amps controllers for a 15 ah ping.
The fastest selection of the Mac will be faster, but a bit sluggish off the stop signs if you choose the really fast wind. I'd say go for 8t, rather than the 6t. In fact, most find the 10t fast enough.
But I wasn't thinking the Mac, because they cost more, and they can't be overpowered as much as the DD motor later. Fast and cheap, to me that says get a 2807 winding dd motor, and give it some volts.
The faster winding dd motor is what I have on some of my bikes. One, I had going 47 mph. They don't last long overvolted that much, but a 72v 20 amps controller works just fine with this size dd motor, and will get you 35 mph. That's 1500w, but the dd motors can take 3000w for short bursts.
A typical dd motor in the faster rpm will reach 27 mph on 48v, but try to get a controller that can do 48v or 72v at 20-25 amps. Then once you have your 48v pingbattery, you can still experiment with 60v or 72v with additional batteries, even such as a cheap sla.
