This topic has been discussed thoroughly in the recent past and there are many opinions on the subject.
I think the biggest determinant is what you want for your genealogical data. If you are interested in finding a lot of people and putting it in an online tree for all to see stick with the Ancestry tree and don't bother with the software.
If you are really interested in researching your family then you will need some software to help you organize your data on your own computer. Doing research it will take you to many places where you will not have internet access. Places like cemeteries, library, archives, public streets in front of an ancestors home, etc. Only if the data is on your own computer will you be able to access that data to answer question that come up in these locations.
I have used my computer in all of the above mentioned place to answer question. One example of the public street was when we were photographing a great grandparent's home. The current owner curious about who was taking the pictures of his house came out. I used my the family data on my computer to help him with the history of his home that he was restoring.
I use Family Tree Maker 2012 to organize my data. While deathly slow, it does a good job in handling the data and creating the reports and charts I need. It will sync with your online tree, but as I understand it is a slow process for the first one and not very fast for subsequent ones. (I do not have an online tree as after 10 years my families are still expanding. I will put it online when they become more complete.)