If I was switching over from the infant seat to a toddler seat here are a couple favorites I might choose and why. There are so many more choices now then even just a few years ago!
The Britax Boulevard sets the industry standard for safety. A five point harness, side impact wings, and both the HUGS AND LATCH systems make this one hard to beat. If there is no price too high for your child’s safety or your own peace of mind, stop searching here. You can use it rear facing until 40 lbs! (My little girl is 4 and weighs only 37 lbs.). And the forward facing until 70lbs. Britax also has a wonderful quick-adjust harness which I'm not sure most people understand until you actually have used it on a regular basis. But trust me it's great!
The Sunshine Kids Radien80. This one folds well, has a great shoulder strap, and is certified for use on aircraft. It’s narrow width lends it to many uses – in addition to air travel. And fits 3 across in the back seat of our SUV much easier then others. This is a top-notch choice when used in forward-facing capacity. You can use it rear facing until 45 lbs. and forward facing until 80 lbs. The fact that you can be safe and still fit 3 across is great because once your kids are in pre-K and Kindergarten the play dates begin and with 2 kids I still have 3 car seats in the car because of how often we have an extra child in our car.
The Britax Marathon is durable, comfortable, and considered one of the best forward-facing convertible car seats in the industry. If the comfort of your child is your highest concern, your search may be over. And it's a bit more affordable then the Boulevard. It's good for rear facing up to 35 lbs. and forward facing up to 65 lbs. (My 6 year old boy only weighs 47 lbs.) If this car seat was an option for us when he was younger he'd still be in it! But we had a smaller sedan at the time and he was 20 lbs at 6 months so we used the Britax Roundabout since it fit rear facing nicely in our car.
Here are just a few places you can check out reviews from:
I also came across this nice article on BabyCenter.com on how to buy a car seat.
And remember you can check SeatCheck.org to find a car seat installation location near you!