I think I have some proof if you rode my bikes.
I have 2 bikes that use the rear internal gear hubs driven by chains from a motor mounted mid frame.
The Charger bike is one, and my home built Speedmachine is the other.
Check here for pics and specs.
http://www.evalbum.com/1262
I also have an E-bike that uses a rear hub motor to compare.
First of all, most ICE have a horsepower and torque curve that will peak in a certain RPM range.
So using a transmission will let you take advantage of that and give you the best of both worlds, low speed torque and high top end speed. Use a single speed transmission and you get one or the other.
Electric motors on the other hand have very good low speed torque that can be flat across the RPM range.
Given that, its not as necessary to use a gearbox to get good acceleration BUT, you are usually limited in top speed, say 80 MPH (for a car). Also remember that usually a good 3 Ph AC motor used in electric cars are geared down (10:1) and have an top RPM of 10,000. Much more than an ICE.
Crystalite hub motors break down their hubs in speed ranges.
http://www.electricrider.com/crystalyte/index.htm
You get low, mid or high but you can't have it all.
Now comes the transmission.
Since I'm using the existing gearing, I'm not adding anything else except for the motor and gear reduction.
Ecospeed has a good page to read about gearing.
http://www.ecospeed.net/gears.html
I can have my cake and eat it too.
I have the ability to use my motor throughout its RPM range and then up-shift, so I can use the low speed torque and then the high RPM horsepower. Once I run out of RPM, I up shift to use it all over again.
Its the whole reason you use gearing on a bicycle. Just think if you only had one speed, and some bikes do! You have a low gear beach bike that goes maybe 15 MPH max or some of you who ride a single speed track type bike (with brakes!) and have very little low speed torque. Not too good on hills is it!
So in a nutshell, I don't like hub motors. Sure, its an easy way to build your own electric bike, nothing to it actually, just install the hub and wire it. Unlike building my bike, you have to have room for the motor, make mounting plates, figure out the gearing, bearings, freewheels etc, BUT, yes another but, you are not dragging along the motor as you are in a hub that is always turning! Plus it takes more power to rotate that heavy hub. So lots of pros and cons, but the way I see it, well, its the way I built it. And I'm still going to add improvements to my Speedmachine..
Oh BTW, the Charger bike is plenty fast too, even though it only uses a 1/2 horse motor. I can accelerate from a stop signal and hit a top speed of about 30 mph on that bike, and it climbs hills really good too! Can't do that with a hub motor... Oh and the Charger bike is very quiet.
My Speedmachine has a little gear whine from the planetary gearbox, something I'm working on...
Sorry I forgot, the E-bike. It only goes 16.5 MPH, even while trying to peddle! I like to go at least 20 + mph. I has fair acceleration but not like my Speedmachine, not even when the Speedmachine is at 35+ mph, its still pulls better then the E-bike at 5 MPH!!!