Which is better: the MR3020 or the MR3040?

Which unit should I buy?

Is the battery in the MR3040 the only difference between the two models?

Besides being a little cheaper, is there a reason to buy the MR3020? Better range? More features?

On Amazon, the 3040 is only $4.50 more than the 3020, so price is not a big consideration.

Thanks for the advice! I'm looking foward to joining the PirateBox community. I'm hoping to install mine in a coffee shop.