Sooo...
I work for an insurance co. I can guarantee you if the car is ever totalled, the value the insurance co. will assign to it will not be Kelly Blue book, but probably a local market survey and it will most likely be much less than you expect. (I handle about 3 totals a day and very rearely are the people satisfied with what they get...insurance in my state does not cover replacement of the car, it just covers the actual cash value of the car). If you are concerned, ask your insurance company up front what value they use if the car is totalled and ask them to get you a figure.
I'd personally always take collision coverage. It's worth it. That means you will be covered for repairs to your own car in an accident. It does not matter if you are at fault or not.
If you do not have collision on your policy, even if the other party is at fault, your insurance company can not help you. Your only choice if you do not have collision is to go through the other party's policy. This is often a big headache and expect to get less than 100%. Maybe 50% if you are lucky unless it is extremely clear cut (ie. someone rear ends you, or hits your parked car and even then, don't be so sure the other party won't fight the accusation or lie).
Liability Only will only mean that the insurance co. will pay out damages to the other party if you happen to hit someone and are considered at fault.
Some states/insurance companies offer limited collision on policies where they will ONLY pay damages to your car if you are clearly NOT at fault.
Here is an example from my job last week. IV = the person insured with my company. OV= the other party.
IV and OV have a collision. IV claims that she is in the right lane with her right blinker on. As she goes to turn right, OV passes her on the right and she turns into her. Passing on the right is not allowed in this state.
OV calls me up in hysterics, crying and screaming because she does not have collision on her policy with her carrier. She expects my company to pay 100% of her damages. I ask her her version of events. She tells me that she was in the right lane and IV was turning from the left lane and hit her. She says she was not passing at all.
So now I have two different stories. I get pictures of the road. I get police reports. I ask for independent witnesses who know neither party. The way this road is set up, either way could be feasible. There are not witnesses. There is no police report. I look at the damage on both cars. It could have happened either way.
To be fair, I offer OV 50%. OV FLIPS OUT swearing and crying and screaming. I cooly advise her that she has absolutely no proof that it happened how she said and that I have absolutely no proof it happened as my IV said it did. Therfore the only fair thing to do is offer 50%.
Crying and talking about lawsuits, she hangs up. She can't really sue. She has no proof. She's stuck with 50%.
If she had collision on her own policy, she would not have to deal with it. Now she's on the hook for 50% of her repairs.
I get claims like this a lot.
Having collision on a car is worth it. Even if you are a good driver. Sit with your agent and have them go over your options.