Okay, I got 1 physical product that ships worldwide.
I just need an order page where people can order in quantities.

So all the people need to enter should be name, contact info, shipping address,
credit card details and quantity.

The payment gateway is authorize.net.

The goal is to keep the order process as simple as possible as
the demographic of the product might not be very web oriented.

Is cube cart appropriate with this?
Which version would be better if so?

Truthfully, cubecart is more than you need for this. Not sure if authorize.net has a build a button tool or something as I've never used it, but you could use Mals-e.com or paypal to just build a simple cart button and put it on your order page.

I've edited the signature, as it contravenes forum advertising rules.

Also, in regard to 1 product stores, refer to this topic posted previously...

http://forums.cubecart.com/index.php?showtopic=33566