Can I ask then, if you don't do anything differently with your unvaccinated son, is it because you trust the people around you to tell you when they are sick, or you believe the actual exposure/catching rate to be less than what the hype would have you believe, or you have faith in his body to be able to fight any problems?
Firstly, these are just my opinions and what works for us. I'm going to go with option A and C and I'll give you a D.
So for A: For me it's a fairly easy decision because I live a fairly quiet life, I generally prefer my own company or that of my family (gatherings normally have about 12 people or more, so not small), but I would know if they weren't well, or had been off. I try to make it so that we spend the bulk of our time at home, apart from the school run, we only go out 2-3 times a week anywhere else at most. He doesn't get handled by other people than family that often.
For C: I do have quite a strong belief in his body to fight of sickness. Most of my friends who have had kids at the same time have already had one or two colds, that often last for about a week. They think this is pretty normal - I do not. DS is 8 months and has just had his first runny nose. DD and I have had colds this last week, so I thought he was coming down too but it hasn't eventuated. I'm now unsure if it was actually just related to teething as it only lasted 2 days and since the day after he has the typical red cheek. He's yet to be sick, even though the rest of the family did catch whooping cough when he was only 2 months old. It was a rubber meets the road time where I questions myself, but it wasn't an issue for us.

D: It takes a little from option B. I think some of the diseases aren't as likely to be caught by my child - polio, diptheria, hep b. There are others I also don't think are the boogey man they are made out to be unless said person who catches it has an underlying condition or issue - measles, mumps, chicken pox. The main ones that I think are the threat they are said to be is Tetanus and Whooping Cough. But the WC vax misses many strains and is mostly passed through long exposure to adults, vaccinating babies for it is the wrong target IMO. The tetanus is the only vaccine (with vaccinations current formulas) I would consider to get a vax for, but as my little man is not mobile at the moment I haven't made any decisions on that one in particular yet. If I did do it, I wouldn't do it until after two year old and I would do a blood test and stool test to check his immunity first.