I had fitbit and it had issues for months that were never resolved. So I ditched it and bought a garmin only to find they have software issues too. I think that both companies do not have the infrastructure in place for so much data to be processed. I do not know of one that is better at this point.
Fitbit uses software in your computer to give graphs unless you want to further passed it on.
Garmin uses their web to do the math. it is more of a problem when their web is un connectable.
I have/had/had/had trouble connecting to garmin connect.