[Alpha]

Well, in terms of security, Apple's iOS has been tested and found to be the most secure in terms of internet and the like (so the iPad being the tablet extension). However, it lacks versatility as most other tablets do in being able to install anti-virus on them.

It is worth noting that viruses (from my understanding) are designed to attack through a specific browser or system of information delivery so as to interfere or interact with an Operating System in a pre-set way or to receive commands. Tablets are still a niche in the web-browsing base as it stands, but it is growing so it is possible that more viruses will be creative or adapted to attack them as well. Currently, it isn't as much a deal to worry about as it would be with a laptop however. Especially since there aren't any true "viruses" in existence for tablets for the time being.