I have just installed Windows Live OneCare Beta 1.5.1785.18. I was in the past using Windows Defender. I have only really tried the TuneUp and the Protection Plus.
My problem with the OneCare Tuneup is that it doesn't really do much and what it does do it doesn't tell you what it is doing, for instance when defragging all it said was "C:\" only at the end of the process did I find that it did not do it because it didn't have enough space. It would have been nice to say how much space I needed!
Additionally the only thing that the Tune up does in relation to tuning the system is to defrag the drives and also remove some redundant files. It sounds like it should be tweaking system settings to make sure that I am getting the optimal performance out of my system. With the Microsofts recent purchase of SysInternals I would liked to have seen things like the Registry and Page file defragmentation, however I have no idea if it does this at all [note to MS: make it so that we can view more detailed information about what has happened.]
I suppose on the plus side, it does the things that I should do manually, such as defrag and check for updates... and the firewall alerts in the protection plus are useful to see, but if that is all that it does then I am not that impressed. It is not even a "not seen or heard" application because it makes a mince meat of my system resources when it is running!
There is an activation portion of the program too, but because it is Beta it says not to activate it, however I don't think I would want to pay for this application at the moment.