I found the ergo great for short periods of time, but my shoulders would start to ache. The advantage of a mei tei is that they are a more flexible in how you do them up. For example, in a back carry you can either cross the straps at your front or wear them backpack style.

If you're buying on ebay, beware of fakes, especially with ergos. Babes In Arms have info on what to look out for and also list authorised retailers.