1700KV is primarily a 5S motor.
You are under the misconception that 4S is bigger than 3S - only so if you just add an extra cell. Taking a 3S pack and a 4S pack that have the same
power, one should be no bigger than the other. A 3S 6600mAh pack has the same power as a 4S 4950mAh pack. They should offer the same run time when combined with an appropriate motor and gearing.
In fact, a higher voltage set-up will give a higher efficiency, assuming that the two set-ups are geared for the same speed, therefore the higher voltage will give a slightly longer run time. This is why you run lower KV motors on higher voltages, and higher KV motors on lower voltages, to achieve approximately the same overall motor RPM, then use the same gearing to get, say, 40mph. They use the same power as each other - the same job is being done. However, the equation Power = Current x Voltage, shows us that the higher voltage results in lower current, which means less heat, and therefore higher efficiency - less power is wasted. Therefore, the lower voltage set-up will use a tiny bit more power - and so the run time will be longer with the higher voltage.
Have a read of
the guide, then I'll help with anything you don't understand, or have problems with.
The Tekin is fine, as is the MMM. For higher voltages (5S, 6S) definately go with the Tekin, for lower voltages (3S) go with the MMM. The lines fade with 4S, and either will do nicely - though the Tekin may just have the edge - but it is more expensive and the motors are more fragile. Conversely - the MMM's case is poor as it may split unless braced, and the fans are weak.