I've been in the insurance bidness for 20 years. It all depends on the company, the adjuster(s) you end up with and what the other person claims happened. If you were in a head on then that is something which can possibly be disputed as to who was at fault. It just all depends on the details. If the tangible facts & testimony from everyone make it clear that the other guy was at fault and the other guy has insurance then I'd start out dealing with the other company without an attny.
Here is the only thing to really remember in that case: DON'T SIGN ANYTHING until you are satisfied that you are either exhausting his limits (and you don't plan to go after him personally) or all of your bills & other claims are covered such that you are happy with it. FYI you won't be paid for anything until you sign something too. Though you can usually settle the car damage independant from the bodily injury.
If you think you may have permanent damage and the guy has a high limit policy or he is a wealthy individual, then get an attny.
If you try to deal with the other company and you feel they are giving you the run around or trying to low ball you or if there is any dispute as to what happened which could place any negligence on your part then I would consider filing through your own auto insurance & letting them handle the situation and/or getting an attny.
There is your advice, consider it worth what you paid for it. :wink: