The difference between CD and online function is that online hides the internal forms and worksheets, which can make troubleshooting difficult. But, online has cloud backup. And if you call customer support, online can see your file as you work on it and can show you what to do. The CD program gives you more control over your data and you can make manual adjustments if needed. But there is no backup, you are responsible for your own backups if something happens to your computer. There are two procedures for customer support to look at your file when you are using the desktop version, but it is a bit more complicated, and one of the methods may not work with Mac.
Price-wise, online and CD are similar if you are only filing one return, the CD program is probably cheaper if you buy from a third party retailer like Amazon, Staples or Costco. Amazon and Staples also sell digital downloads if your computer doesn't have a CD player. The desktop version is definitely cheaper if you need to do more than one return. If you filed last year using the online version, there is a way to download your 2015 file to your computer to get a head start by pre-loading last year's info.
Turbotax Deluxe on CD or download will have all the forms you need for your situations. Turbotax Premier on CD or download includes a higher level of telephone support ("answers from CPAs, a $19.99 value").
Of course this forum is always free, although not every question gets answered due to volume (5000 questions per day). Be patient, and if no one answers your question after 24 hours, ask it again so it goes to the front of the line.
Otherwise, take your time and go through all the steps one at a time, and don't be afraid to ask for help.
