Sigs are nice guns, very nice. I am quite fond of the Elite series in particular. The stainless versions are noticeably heavier which may be a factor if you want to use it in competition.
Now that being said, the P30 (and P30L) represent the pinnacle or pistol development for the entire industry. The ergonomics are second to none and are quite unlike any other pistol out there. The interchangeable backstraps and side grip panels allow for a truly custom fit. The durable polymer frame makes for a very lightweight gun that still manages to have fairly minimal recoil. My preference is HK's proprietary LEM trigger, but many shooters are partial to the traditional SA/DA trigger of the V1 P30.
To truly appreciate the P30 design, you have to hold and shoot one. I'm confident that you will be sold if you get the chance to shoot one.