It is MUCH better (and no wasting juice) for the FIRST fill, (you don't need a syringe to "top off" but you can easily fill from the bottom up - very important for vg or high vg juices) Once I got over the "needle" part and actually tried it I never looked back.
I don't know if the syringe method is better just different. I personally prefer to just drip along the wall of the carto as I spin it. I don't want to carry around a syringe to refill or top off while on the go. I tried the condom fill method didn't like wasting the extra juice that I would have to blow out from the carto. Just my preferred method.