The best software differs from one person to another. If you must have a software that will sync with Ancestry.com you will have to use Family Tree Maker. There are good and bad things with any software.
I would suggest staying with one that has a regular history of updates and is well supported. I wouldn't want the software to go away in the foreseeable future, as it is painful to switch. You essentially marry the software you decide on.
You can try Legacy or Roots Magic via trials, they are both very good. Family Tree Maker does not have a trial. There are two programs for people who don't mind complex software and want the most power possible: GRAMPS and The Master Genealogist. GRAMPS is free and is regularly supported. TMG has a trial and has great support. These last two can be overwhelming if you are not a computer person.