well, i did see people drinking over their desktops too... I wouldn't necessarily call it much safer, it really depends on the person ( he can still knock it over and have the thing smash to the ground you know ). 🙂
i doubt anyone can properly estimate the life expectancy of either machines... Instead of wasting time thinking about it, why not try to define your needs first? Do you care about portability? Do you care about a larger screen? Do you own a table at all? 🙂 once you can answer these and similar questions, i think the choice will be quite an obvious one.