I think a lot depends on what your expectations are. Are you looking for a mature deer, are you looking for meat in the freezer, are you looking at public land deer or are you hunting private land? And if you're hunting private land, how many acres and what are the management goals (if any)?
If you're looking for meat in the freezer, then I think you'd be better off shooting a mature doe. You'll get more meat than a 1.5 year old buck anyway and a mature doe is going to be more challenging to shoot anyway.
If you're hunting public land, then it's a crap-shoot. If you don't shoot a spike buck, there is a good chance that the next hunter the buck passes will blast him. But, by the same token, if no one does shoot the buck, he'll be just that much bigger next year. And little bucks do survive to become bigger bucks.
If you're hunting private land, then you have to ask yourself some questions before squeezing the trigger. Are you seeing a lot of does and few bucks? If so, then maybe you need to thin down the doe population a little bit. Are you seeing a lot of immature bucks? Then it's possible that one or two small bucks harvested won't do any long term damage to your management plans, but it's a sure thing that a buck in the freezer isn't going to get any bigger. And one of the biggest factors in antler growth isn't genetics (although that does play a factor), it's simply age! A spike buck at 1.5 years old might be a fair 8 at 2.5 and a REALLY nice buck at 3.5 - 4.5 years of age. But if you shoot him at 1.5, you'll never know.
So it all depends... This fall, I hunted property that I've been asked to manage the deer population on. The landowner is interested in nice, large, symetrical racks on the bucks roaming his property. So when I saw a spike buck walking through the open, and he had a deformed antler, I shot him. BUT, here in Tennessee, we're allowed to shoot three bucks (regardless of weapon) throughout the season, so I knew I wasn't utilizing my only tag. In Wisconsin, I probably would have let him walk, even on public land...
Formerly Steve @ G & S