It doesn't depend on how much you drive, although it may depend on where and how you drive. I would argue that the best use for almost any vehicle is to use it until it is worn out. If it is running when you sell it, the next person is going to drive it, not scrap it. There is a very large 'embodied energy' in a car. Energy used to make the steel, run the factory, ship it to you. SOMEONE is going to finish using that car up. If it is to your economic advantage to be that someone, do it.
If you are comfortable with this, then the next concept is that it's better to own or at least use the most appropriate vehicle for the task at hand.
Example: Right now our household owns a subaru outback and a chevy silverado. The subaru gets almost 8 times the yearly miles on it that the truck does. But the truck can haul a lift of plywood or 100 trees in #2 pots. (I'm a tree farmer)
If you have room, then your best strategy may be to keep the accord as being a roomy enough car for holidays, buy a hybrid for the daily commute.
Medium efficient car vs small inefficient car.
Look at the total lifespan of the vehicle. Depending on the numbers, the Medium car may be overall cheaper. Or not. As a rule of thumb buy the smallest car that will do the job. But don't blind yourself to a used car. Also look at the lifespan of the car. A cheap small car that has to be replaced at 100,000 km is not a win. Consumer Reports is THE goto for this sort of information. They have figures for TCO for the first 5 years of ownership of almost every make out there. While there is a difference between 5 years and TCO the first is a good indicator of the second.
Hybrids vs Diesel
The Europeans are getting good at making small diesel cars that get better gas milage than hybrids. This is a multifold win: Diesel is easier and less energy intensive to make than gasoline. Diesel gets better mileage = less carbon burned. Diesel engines tend to last forever. Unfortunately these cars are not marketed in North America, mostly because they require lower sulfur diesel.
Hybrids vs All electric
Where does your power come from? If you are using coal fired generators to charge your car, you are only exporting your carbon footprint. And over all coal is worse than oil this way. In addition at this point the technology used for all electric isn't sustainable. There isn't enough lithium to make all the required batteries. The hybrid uses batteries only as a load leveling device. Overall the engine runs more efficiently at a more constant speed.