I have both books but not really studied the swimsmooth one yet.
The total immersion book i have is a bit out of date in comparison with the DVD, I believe they have updated some of the methods on the DVD as they found that people were taking them the wrong way.
I think both systems are good and will help a beginner swimmer, but I prefer the swimsmooth system, it seems less prescriptive to me, for example the TI method will have you look at the bottom of the pool, The swimsmooth system will have you try looking at the bottom, ahead and in between then doing what works best for you.