It's probably a matter of preference really. I have had both. I prefer the wireless. Currently have a Filzer dB4LW wireless. It was cheap and it works. Here's my take;
Wireless - obviously no wire to contend with. Sensor is usually slightly bulkier as they need to contain bettery and transmitter to send signal to computer. Eventually will probably need to replace battery, but should not be a big deal, and should not cost very much. Wireless is also a cleaner install. I like things to look good, and can't stand dangly wires all over the place... wrapped around break cables etc.... I have also since purchased a Polar heart rate monitor and don't seem to be getting any interference with the transmitter from the HRM or the computer. Bonus.
Wire - wire casing tends to dry and get brittle over time since cycling does expose it to the elements. When this happens (and it will), the wire may break and you will need to preplace the sensor. Most are replaceable, but you will need to order from somewhere and it will cost you some $$.
Whatever you end up getting, calibrate it with the roll out test. Don't use the charts that come with you computer...
My next cycle computer will again be wireless, have a HRM built in, and will also probably measure cadence. You should also know that I am a data junky!
Before I die, I will have one with a power meter!
