Asking for the best software is like asking what is the best car? You're quite liable to get a whole range of answers. There are only 3 packages for this - FreeScan, ProScan and ARC-XT
I would start off with FreeScan, which is freeware, then move onto ProScan or ARC-XT at some later time if you need their capabilities. All the authors can be found here, and in fact ProScan has its own sticky thread for support.
This article gives you all the links you need...(all links are blue)
Uniden DMA Software Support - The RadioReference Wiki
and this article will get you started on how to understand how to program the DMA scanners, USB-serial cables and much more. Find your scanner at the bottom of this article and read the Easier to Read manual - don't bother with the Uniden mess...
Program your DMA Scanner - The RadioReference Wiki
Mike