Both brands are decent.
I know a lot of people swear by both.
The only thing about that Beco I don't like is that it offers a Forward Facing out option. It means the baby has a narrower seat, and is forced into quite an unnatural position. It also puts more stress on the parent's back. That said, it's still a far better option than a Baby Bjorn.
Do you know if there is a Slingmeet nearby you? You might be able to try one out before you buy then.