Pros: Good balance, reliable, good looks, single-stack makes it fit smaller hands ok, accurate, smooth operation.
Cons: 8+1 rounds, long trigger reach, heavy DA trigger pull, requires slide pins be replaced every 4 or 8K rounds [breach block is pinned into folded metal slide], stock magazine base plate feels awkward, if a true P6 it may be be in rough condition, funky notch in hammer, some complain about a slightly higher-than-desired bore axis, sight POA/POI takes some re-learning for the SIG system.
The P6 was the military/police sidearm version of the P225. I have a great P225. I've had sig do some work on it, installing short trigger and short reset trigger. It is the smoothest DA/SA I've shot.
This pistol is pretty accurate, but a 9mm 1911 is probably more accurate. So, for a range bullseye competition gun I wouldn't get it.
This pistol is pretty compact, but it only holds 8 rounds of 9mm. My Kimber Compact II 1911 holds 7+1 of .45 in about the same size. My S&W M&P 9c holds 10 [I'm in california: free states 12] in a pistol that is the same overall size or smaller, and just as accurate.
In other words, this is a fun gun that is a joy to shoot, but it depends on what role you have in mind. If you want to do CCW, then there are more compact 9mm that carry more. If you want to do bullseye, there are more accurate ones out there. My Baby Eagle Full Sized 9mm holds 16 and is more accurate, but not as easy to carry.
There are better options for almost anything you'd ask a 9mm to do.
That said, these can be very sweet guns and I enjoy mine a lot.