It's funny when people state that "this will be my only gun for a few years."
It's like saying, "this will be my only shot of heroin for a few years."
Be warned, you are starting down the road.
That being said, are you sure you want to spend the $ for a Sig or HK right off the bat? I have an HK USP .40, my third gun, and it is pretty sweet. But what was sweeter is that I knew enough about them to buy a high-quality used HK.
In the end, be comfortable with the grip! My first was a Glock 17. I never thought to compare it to the 19, which for my hands, is a lot more controllable.