Wilson is 14 months, unneutered. I don't plan on neutering him until he's much much older... to diminish prostate risk at a TBD
We actually had a neuter appointment scheduled for him at 11 months. We decided not to neuter because:
he's the friendliest dog known to man
he's never marked inside the house and shows no intention of doing it
doesn't hump anything
he proved that he has an excellent nose for hunting and we don't want to discourage that
he's primarily a house / companion dog and he's got the best disposition. At the end of the day, I didn't want to risk putting him under for a surgery that he doesn't need. I wouldn't do that to my husband, myself, or my child... why my dog?
We have gotten a lot of push back from other people who don't understand why we won't neuter him. It's annoying (esp since we depend on our dog walker who is a big proponent of neutering), but because we have none of the aggression/marking issues, it's hard for her to make a case for neuter. I also want to note that a lot of people claim that neuter will change those behaviors - I have also heard 1001 times over that neuter won't do anything if your dog is aggressive/marker, etc... once those traits are displayed.
The biggest pro to not neutering your pup is that Wilson is also much more filled out than most other vizslas we see. Our friend has a pair of vizslas that were neutered before 1 and they are tall and lanky. We get lots of compliments on how healthy and manly Wilson is starting to look. He's really filling out and deepening in the chest. I'm thrilled that he's getting to grow and develop the way he was intended to.
Finally, I find it really odd that we live in a society where people brag (yes BRAG) that their male dogs still pee like girls. Is that really a good thing?!?! Evidently, yes. This is a totally tangential comment, but that helped steer me towards the direction of not-neutering Wilson. Frankly, I got tired of hearing from everyone about how we SHOULD do it without any reasons as to WHY its beneficial or necessary.
Good luck with whatever you decide. These are just my 2 cents!