Point Number 2: Both Firefox and IE have a few security holes info on which is available at www.secunia.com. The most secure browser at the moment seems to be Opera (not because it has the least number of bugs, but because its userbase is not as high as IE or Firefox and its code is not open source...therefore it has the least number of KNOWN bugs)
Point Number 3: Browsing speed - to an extent, Opera is faster than others because of better handling of cache. Loading speed - in Windows, IE will probably be fastest as it is directly integrated.
For detailed analysis, check http://www.howtocreate.co.uk/browserSpeed.html
Point Number 4: I think that the more number of add-ons you have in Firefox, the more resources it may take, and so, Maxthon might be lighter on the resources, but I am not sure... Also, if sys. resources is of importance, I would recommend Slimbrowser over Maxthon...
Point Number 5: Try out various browsers, and use the one you are most comfortable with. Just make sure to have your Antivirus, Firewall running in the background and regularly check for spyware as well...
Maxthon has a very light footprint as compared to Firefox. Maxthon has all the inherent advantages and the inherent disadvantages of being based on IE . So , if you are an IE lover , Maxthon is for you. Else , stick to Firefox .
BTW, is maxthon available with IE7 based engine ?