To bike or not to bike...

I posed a similar question on a local moms message board that I belong to. Here's the more expanded version of what I wrote there:

There has been an ongoing discussion in my house for about a month. My husband and I are currently banging our heads against the wall over this issue. Every few days, I'll come to Husband with a serious, focused expression on my face and say, urgently, I really need to talk to you. His voice will adopt a concerned tone, and he'll ask what's wrong, and what it is that I need to talk to him about, and I tell him and the concern disappears and gets replaced with annoyance. It's about the whole bike thing again.
We are trying to decide if a) we should get something for our bikes so we can ride with Toddler (I guess I can't call him Baby anymore, so we'll officially change it to Toddler on here), and b) if we were to get something, should we get a trailer or a baby seat.
I've been to several bike stores and talked to several helpful employees, as well as one bike store where NOBODY talked to me until I was on my way out the door, despite me being in there for 10 minutes and hanging around the baby seat with the most dumbfounded expression I could muster and I've had mixed responses to the question: What is least likely to kill my child? Some bike store employees have said they'd feel more comfortable with a trailer; some have advocated the baby seat.
If I were to make a practical list, the trailer wins out because:
1. Micah could read his books or have his cup with him on the ride
2. It's lower to the ground, so he wouldn't fall far in the event of a crash
3. Many trailers turn into strollers, which would be practical for things like biking to local museums or parks or farmers markets
4. Many trailers have some sort of storage space
5. Trailers can seat 2 children
Despite all those pros, instinctively (having never tried either), I am more comfortable with the seat. Having biked to class the first week, I noticed that I did a lot of maneuvering on and off of the sidewalk, and I think that would be lost with a trailer. And I think maneuverability will be key when riding in the city, which is what we would be doing. The sidewalks on many parts of A Very Busy Street don't seem like they'd be able to accommodate a trailer, and I don't think I'd be comfortable riding on the road on A Very Busy Street. From my neighborhood I'd have to be on A Very Busy Street for some amount of time. Plus, each day we become more and more sure we're done having kids, so there's not really a need to transport multiple children.
So despite these concerns, we're still having a discussion as to whether or not we should get something. The pros are:
1. We could ride to the grocery store, library, farmer's markets, museums, parks, rather than drive
2. Exercise
3. We'd be modeling to Toddler in some small way that we don't need to be completely dependent on cars. I think that if we start showing him now, rather than when he's 8 that there are alternatives, it might end up being the norm for him.
4. He'd probably enjoy it (Husband interjects: He'd probably enjoy playing with knives as well, but we're sure as hell not going to let him play with knives.)
5. My mother is an avid biker and baby seats and trailers are designed to easily go from one bike to another, so it's something she could do with him as well
The cons are:
1. He could die
2. He could be horribly injured
Neither of us wants to be responsible for the death or injury of our child, especially one that we could have prevented. And the death or horrible permanent injury of my child is certainly a catalyst for my crippling anxiety and a good argument for prudence. But, I also don't want to live my life in fear that something I do could possibly be terrible for my child. If you break it down like that, there are so many reasons not to do anything, a gazillion reasons to stay indoors every day. I spent too many years living like that, and I'm working very hard to stop. It's certainly not the life I want to live or model for my kid.
I have found the following websites http://www.whycycle.co.uk/cycling_with_children/baby_carrying_seats/
http://www.ibike.org/education/infant.htm
that address some of my concerns, but we're still not convinced either way. We're not risk takers over here, so doing something like putting Toddler on a bike would be a huge step for us.
This is the sort of thing were prayer and logic elude me. Should we give up the idea because we can't come to a consensus, or should we be persistent? Do the cons win, or are the pros worth risking?