If you're sure you want a true "double" that is lightweight, the Latitude is terrific (the best!). I have found that unless you have twins or your children are closer to a year apart, the double is limiting. I prefer the Phil & Ted's with the jumpseat for a toddler and newborn. That way you can go back and forth from single to double (this was great for me when my son was at preschool and when he was older and didn't want to be in the stroller, etc.) The Phil & Ted's does have the attachment option for the infant carseat. My favorite is actually the Valco Runabout with the jumpseat, but with the jumpseat you can't use the carseat adapter (I use a european carrier with a convertible carseat, not an infant carseat carrier, so it works for me).
I actually do lectures on picking out strollers because I own a stroller fitness company and many companies let me try out their strollers, so feel free to e-mail me if you have any questions.