in general, wireless mice have the potential to fail before their wired cousins. this is due to the fact that they use rechargeable batteries. my 5 year old logitech wireless mouse's battery is a complete pain to deal with (i gave it away free). it still works but the battery life is horrid nowdays.
i have the razer deathadder myself and its a fine mouse. the two are built similar but if you don't abuse it the deathadder should last longer granted some random failure doesnt happen.
function better? all mice are a personal decision. the most important thing is ergonomics. find a mouse that fits your hand great and is comfortable to use, this is the number one thing to do.
personally i'd get the deathadder.