First SIRF3 chip still supports NMEA and is a better/faster/slightly more accurate chip. Not a lot in it to be honest but as its getting to be the most common out there don't shy away from it.
I use destinator via freedrive. Reason being its easier to set up and in my opinion has better routing for where I am. Down side is freedrive or mapmonkey still only support destinator 3 which is 2004 map data. That said IG map data didn't look any newer when I tried it (same roads were missing). Both are no longer current products although you can still buy IG for however long their stocks last. You cant buy a new copy of destinator 3 any more and none of the newer versions to my knowledge will run on a PC. That alone might mean you have to use IG unless you get creative
Nothing to do with your question but I am currently looking for an alternative but that's proving to be a bit difficult. I did try tom tom 5 via an emulator but on my sp13000 it ran too slow but tom tom is really good. If only they would do a proper PC version we would be laughing in the UK.