I own the P89 and have held and felt the trigger of a Sigma. I think the Ruger is a better made gun than the 9V and is better built. The P89 has a longer track record to, FWIW.

If you go with the Ruger, try to find an all metal (other than the grips). I recently found they made them with a polymer frame, but all I have actually seen "in person" have been aluminum.

As for accuracy at 25 yards, they should both be able to kill a wattermellon without missing more than a couple of times. The P89 will!!

I cant commit on the P89--I dont have one of those but I do have a Sigma. And I can tell you that I hate that pistol. The trigger is way to hard and doesnt feel good at all but that being said I've shot well over 1000 rounds thru it and it has never miss fired or jamed not even once. I'm not as accurate with that pistol as I am with my beretta or taurus but I dont think its the gun, I think its the way the gun feels that makes the accuracy not as good.

Another P-89 fan here. I purchased the gun used and have put at between 4000 and 5000 rounds through it without a single hicup or replacement parts. Used it in my first IDPA match and scored middle of the group. Took it to my Texas CHL course and kept all but one of the rounds in the 8 and 9 rings. That said, I'm thinking of trading it and another gun in for a new SR9c. Gotta keep at least one Ruger in my family!