Which is better, the MR3020 or the MR3040?

I'm going to make an OpenWrt PirateBox, and I'm wondering if the MR3020 or the MR3040 is better. The MR3040 is a few dollars cheaper on Amazon, so I'm wondering if there's any reason to spend a few dollars more to get the MR3020, or vice versa. Thanks!

technically the 3040 is the 3020 with a battery and slimmer profile.

In my usage I've gotten my 3040 to last about 4 hours on full charge and using a USB stick for storage.
the 3040 also has the advantage of being pocket-able with a low profile usb.

such as san disk low profile usb

I picked up mine at Walmart in the us for about $40 including tax. so there is that if you don't want to wait.