Of the two you listed, and for your intended use, I say without question, go with the SD9. This is your first gun, you will like, and shoot, the larger frame gun better. The SD9 also has a much larger mag capacity, I like that for both home defense and the range. Once you get more practice and more proficient, you will shoot a smaller gun better. I just wouldn't start there, especially if you're getting it for HD and range use. Just my opinion...

Now, I don't own the SD9, but I do own the Shield 9. I like the Shield, decent trigger, and a good shooter. I have picked up an SD9 at the LGS, and it is a surprisingly nice gun for the price. Good looking gun, too. I expecting an absolutely horrible trigger like I've experienced with the Sigma. But, the SD9 actually had a pretty good trigger...! A little long for a striker fired gun, but not gritty and super heavy like the Sigma. I actually liked the trigger pull, and think it would do well in terms of providing ability to be accurate. If you don't like it, it's a cheap fix to improve it, but based on the one I tried, I don't see why you'd bother.

This all said, you can probably find a used M&P 9 for not a whole lot more money. Or, find a nice lightly used Glock 19. I think the G19 is hard to beat for an overall home defense, carry, and range gun... Smith just went and copied the G19 when designing the Sigma. Not sure how well they did in terms of quality, function and performance, as I don't own one. But, people that own the Sigma and SD guns seem to like them. They seem like a great value. I do own and really like the G19.

In terms of money, buy once, cry once. Often cheaper in the long run to get what you really want, rather than buying the inexpensive item first ($X), then going and buying the other item later ($XX), as well ($X+$XX=$XXX)... We all have our financial hurdles, but I can say that in the long run, you will never notice the $100 - $150 more that you paid for the nicer gun that you really wanted. Save and get what you really want.

Good luck with your decision!

__________________
NRA Life Member