We have the Bjorn, Ergo and a Kelty. If possible, I'd recommend to get all three in that order. Bjorn up to ~6months, Ergo up to ~18months and then Kelty backpack there on. We did a moderate amount of travel with these and just know, none of these are FAA approved for use during take-off and landing.
My sons like the Bjorn the most because they can see everything. I like it because I can see the baby. The major drawback, as mentioned several times, is back pain. But I was able to go 3-4 hours fine with a 3mo old... though you don't really want to keep them in there that long. I found it helpful to wear a backpack at the same time.
The Ergo is a step up in comfort for me but my kid don't really like it too much. It also doesn't go on/off as quickly or easily.
My toddler and I are very comfortable in the Kelty... the drawbacks are weight, bulk and getting in/out.
98 Lexus LX470
85 Land Cruiser BJ70
09 KK SportsRV