It is like lots of utility programs, some are flavour of the month for a short while then another one is shown as better a couple of months down the line. By all means run them all... rather that than have your PC browser hijacked or a keylogger get your important passwords. Provided they
update on a regular basis and
you scan with them on a regular basis you should not have too many problems. Unfortunately many people install them and forget about them expecting the program to do the scanning all by itself. Of the ones that are capable of that you then find people stopping the scanning halfway through because it was interfering with their work
