In all seriousness, you need to handle them. What kind of size do you like? I own a P226 (40S&W) and love it. A slightly smaller one would be the P229, which is also an excellent gun. If the P226 is too big and the P239 is too small, you may want to have a look at the P229.
Depends on what you're looking for.. Different Sigs have different features, ie the 232 and 2022 are a lot different than the 220 and 226, etc. Its clear that you want a reliable weapon, and all Sigs do that just fine, but then there are fine details, ie caliber, size, material. But if you want my advice,
When you mention a 9mm Sig three models come to mind quickly: 228, 229 and 226. Personally, mine is a 229. I like the milled solid stainless steel slide, not stamped like the other models mentioned. The 228 and 229 are very simular except the slide cut serrations are wider on the 228 compared to the slimmer 229. The 226 is more of a duty gun. It's heavier and the barrel is 4.4" compared to 3.9" (@ 1/2" longer). The grip is slightly longer as well. It probably boils down to several factors. Size, cost and purpose. I haven't had a ton of experience with Sigsauer, but I've had other brands. Sigs are tanks. I think many other gun owners like Sigs compared to their current auto, but they are more costly. That scares some away. Regarding the 239. For some reason that model does not feel good in my hand. See, touch and feel means a lot in any brand handgun. Good luck.