Unless you are 'technically capable' I'd say DO NOT SWITCH and pay Symantec or scour the web for a better price (like NEWEGG with a 70% off expiring soon) that the renewal fee. Some A/V products can be a bear to fully remove from a system, and when doing so, can damage parts of the OS they linked into, such as the TCP/IP stack.
Otherwise, do your homework, check reviews. Be careful of where though, many on the web are not really 'objective' but are supporting specific ones and the sole purpose is to make those look better.
Places to look for reviews, on-line magazines, web sites that are not affiliated with an A/V producer.
A few such as :
There are more, and some are not only for FEE based products.
One thing you should be aware of about MSE, it has at one point lost its certification, look HERE.
The print issue of the same magazine for April 2013 (which is not on-line) has an article called 'AV Battle' on the cover and titled "Your Antivirus, Tested" and lists/reviews both FEE and FREE products. MSE is included. It got a 6 rating (10 highest), the LOWEST of the 10 tested. The last line, "MSE passes muster for low-risk users, but there are better AV solutions." I'd assume low-risk means people that don't surf and d/l stuff and are careful on e-mails they open. They did test 2 other FREE ones, AVAST V7 (8 rating) and AVG Free 2013 (7 rating) as well and are a better free choice according to them.