Actually it all depends on your preferences.
Both of them are good products.
Both McAfee and MSE has nice detection and prevention rate.
McAfee Total protection 2009 offers more features and options, as it's full system protection suite, whereas MSE is only AntiVirus and AntiSpyware.
So McAfee additionally to it offers 2 way Firewall, Parental Control, siteadvisor, Anti Spam (not sure if MSE has this one or not
) and I think Data Backup.
But I personally found McAfee a bit heavy on resourses and all those additional features of course need more resources from your PC.
MSE on the other hand is very light and easy to use. Recommended and used by a few people in this forums, so you can get support even from here
But dark side of using MSE (not really dark, just a bit disadvantage compared to McAfee total protection
) is that as I already mentioned it only offers AntiVirus and Antispyware. So you will either have to use Windows native Firewall or other third part firewall.
Same goes to features like Parental Control, data backup and etc.
So, it all comes down to you.
Do you prefer to have one even though heavy program to control all aspects.
Or get one light program to control your AV&AS part and get more specialised programs to other aspects of your system..