Absolutely go for the old style one! I have a safe n sound unity and it was the worst thing i bought! The old style are still the highest rated seat for under 6 months (the unity only scored 1 star!), they are also very lightweight in comparison to the new look capsules. I had a lecture from a physio about carrying the capsule around, they really are designed to be taken from the car and clipped into the pram, and shouldn't be carried around a lot. My shoulder still aches from carrying DS around in it and i haven't done it in several months now!

One downside is that the older style capsules can be used only up to 6 months, the newer capsules can be used for longer (mine is 12 months i think) so you would need to invest in a car seat sooner. But, you can hire the old style capsules very cheaply (i did this with DD and it was around $60 for the 6 months? might be a bit more as that was almost 4 years ago).