I've been to previous Mega Concert like Muse and Coldplay at Bukit Jalil, even went to DS Siti Nurhaliza at Axiata Arena.

If ur concert @ Axiata, meaning the traffic is significantly less than BJ Stadium capacity. You can drive and park there, but I've experienced a very² long que in and out. Basically stuck for 1 hour to get out of parking.

The best way is always by LRT (even with less capacity of Axiata Arena) but the Car option is still acceptable alternative if you can dont mind waiting/jam.