I used Bitbucket a lot (before Github change their pricing model, user based vs repo based, we as a company used Bitbucket). I still use it for some private repos and it's definitely good.
For intensive work, we experienced sometimes more failure of their webhooks than we do on Github, wich caused our CI to not be as reliable/fluid as it should be, but that was more than one year ago, I don't know how it performs today.
But for free repo (and if you don't pay, you shouldn't be upset when some webhook timeout from time to time) it's definitely a good product. I haven't used Gitlab enough to be able to compare them on speed/reliability level.