All in all, I found Avis to have the cheapest prices for me, totaling $186, all inclusively, for a 6 day rental of what Avis considers to be a full-size car (which they specify as a Chevy Impala or equivalent).
The car I received was a 2012 Hyundai Sonata, which was a very nice experience, and I am usually the person that would make fun of Hyundais. I guess the Koreans have come a long way in car manufacturing. The XM radio was nice on the long trip too. The car was really surprise-free and easy to drive for the first time. A good fleet car I felt.
Here are some hints and tricks I learned.
1. As with almost all car rentals, there is an extra 15%-20% fee for picking up a car at the airport. I think this is just because they know it's a captive market, so they try to charge you more, and the charge usually shows up later in the checkout process on the online booking system (ie: it shows up at the all-in stage, not the "base" car hire fee). Jerks.
A trick I learned is that you can pickup the car at the downtown site (which is where I was going to be anyway before I actually needed the car), and return it to the airport for no extra charge as a 1-way rental in the same city. This worked out exceptionally well for me, since I wasn't going to be leaving with the car directly from the airport anyway, but did need a ride back to the airport, very convenient now that I could just drive myself.
2. Never pay for the full-tank of gas when you pickup the car, it's only a good value if you calculatedly return the car with nearly no gas, otherwise you're paying for whatever gas remains in the tank when you drop-off the car. Because I declined this, I was obligated to fill-up the car before returning it. I ended up driving a few kilometers away from Vancouver International Airport just to find a gas station, but on the way back to the airport, I found that there's a Petro-Canada in the airport, conveniently on the way to the car rental drop-off place. The gas was even the same price as well.
Lesson learned (well, more like reinforced, I know they're assuming you won't bring the car back running on fumes): Don't prepay for a full-tank of gas at car rental return, and just fill up at the YVR gas station.
3. Not only did my Vancouver Avis car rental not have winter tires or chains (over winter), they don't even have an ice scraper. I was surprised, because I even mentioned that I'd be taking the car to Whistler, but they never said a word about it. It's actually required by law in BC to have either winter tires or chains for a majority of the trip up to Whistler on the Sea-to-Sky Highway during winter, as it can be treacherous if it snows. I highly do recommend winter tires or chains for this stretch of road, as it does go down to two lanes in parts, with no median, and you could have a downhill turn where any loss of traction could result in you kissing a logging truck.
4. Look around for online coupon codes and price-shop. I managed to save a good deal of money by searching for them. It turns out I used some Air Canada Executive Club code or something, Avis never asked for proof of anything, and I don't think any other car rental place does either.
5. Finding the car dropoff place at YVR is easy, just go to the airport as you would if you were picking someone up or dropping someone off and there will eventually be signs for car rental drop-off. The drop-off was a very easy experience.
6. I didn't ask, but I should have: when you go to pick up your car, ask what cars are available for the rate you paid, possibly you may get your choice of cars. Maybe being nice lets you get a free upgrade if you ask nicely. I don't know, but it doesn't hurt to ask. I didn't, and I do regret it after walking through the garage and dreaming about the cars I might have been able to drive (even though I was more than happy with the Sonata after driving it for a while).
7. Pickup and drop-off were relative non-events.