Well I'm giving it a go with the nifty 50 now, finding it is going to be the hard part but I figure if I can keep Delphinus in my bottom left corner then I should be able to get it.
But I'm in the Northern hemisphere so everything may be upside down for you.
Do you have a tracking mount?
If so then I'd go for exposures as long as you can go without too much light pollution orange creeping into the photo. 1 to 2 minutes but really I'd just try and see what works best. I'm on ISO 800 and am using f/4.0 on the 50mm, I have no idea if I would be better served with different settings but it seems to work for me0
If you don't have a tracking mount then probably exposures between 8 - 10 seconds with the 50mm and as high an ISO as you can get away with depending again on LP.
I can't say between the two cameras as I have never used either but I'm sure both will perform well no matter which you choose.