ARM based system have advantage over x86/x64 based system as POS machine on remote site. They're immune from attack of x86 instruction based virus, and lots of dancing bunnies people commonly see won't work there.
Not if you write your virus in Java (which is the most common way of attacking Internet Explorer in 2011 and 2012). All of the logic bugs in x86 are still there when you cross compile it for ARM.
Case in point: look at all the viruses for Android which runs on ARM.