I've had both an LMG and a bolt action rifle for a long time.
I do really well with the 249, but it's more of a show-off piece.
I actually get more kills, more frequently, and more difficult shots with the bolt action rifle.
There's ups and downs to both weapons, you can suppress people with both, and the best tactic for taking either out is the same.
Only major downside is the BAR is limited in the number of people it can engage at once, and the LMG has a harder time running back and covering a wider zone of control.
Either way, its best to be a rifleman first.
And I'll tell you this, one LMG isn't a big threat, but two LMGs is a serious problem.