Electric Bikes - Do i want a 36volt motor or a 48 volt motor?

I am having a Americanspeedster Sidekick 4 wheel bike assembled for me. This PVC bile uses 20 inch wheels. Originally they offered a Sparrow motor for it. I started to order the Sparrow and was told that it was a brush motor and they now offer a better motor. He wanted to know if i want the 36 volt motor or the 48 volt motor.
My limited knowledge of electricity makes me think i want the 48 volt motor for more torque. Am i right? Is there a lesson on batteries i need to learn. Such as does the 48 volt have an exhorbriant price etc?
Any education gladly appreciated.
Thanks for looking.

If it has 4 wheels and you add a motor, legally it won't be a bicycle anymore..
Every state in the US considers a bicycle to have 2 or 3 wheels..
Believe it or not, having 4 wheels (Unless it's a trike with a sidecar), it's considered a car..
I know, stupid! Are you sure you want to add a motor to it?
(Even golf carts have VINs)

Thanks for the heads up. Guess i will have to take a chance or two. Where i live i won't be running the streets with it. Too dangerous. Definitely taking it on the KATY TRAIL in Mo.. I will just go slow and fake pedal if need be.

Ha! LOL :D Sangesf thanks for the heads up, i'm was in the same process as versatile as i was planing to almost the same thing as him

I've always pondered about the bike and the 4 wheels thing, guess now that's clear ;)

So I'll better redesign my custom frame for an ebike as a Trike instead of Quabike? :p

I needed more space to carry extra battery and spread the weight / load onto more wheels to keep the tires properly inflated for a good long ride, i not a big fan of those super long bikes with the extra wheel or cart at the back as i've seen some people use

if i'm gonna have 3 or more wheels i might as well put them to get better stability, as i've tried many setups with heavy battery packs, and in rainy sudden breaking situation the bike always fish tails