Convertible car seat VS. Travel system unit

Dawn
What is everyone's opinion on these two? I like the convertible idea because it takes the hassle out of having to buy different car seats as baby grows, but I love the idea of having the car seat attach to the stroller. The only downfall of the travel system is the weight restriction only goes up to like 30lbs....and on the convertible seat how do you carry them? There's no handle correct???