Go with the GSP as you'll want to do everything with your dog and take them outdoors.

As for male or female, it doesn't matter that much if your going to spay/neuter them. Breeding is a different story. The male will mark stuff but I find my female will find the mark and mark it herself but the mark has to be there in the first place. As to which takes to training better, matures faster, is an alpha, etc. it's all the individual personality. Even if there is a statistical difference, the amount of extra work/time is probably nothing compared to overall training/time.

So if you get to pick one in the litter, pick one that suits you, ie. bold/submissive, active/couch potato, etc.