In both modes (SP & MP) RA mod is better. LwAmi devoeloping was ended 10 years ago. Many bugs never wasn't fixed.
RA is more demanding but gives you better "realism" if you mean weapon and
ship systems working (especially AI systems). Also more platforms to control, much more weapons and more scenarios.
Sentence: LwAmi is better for sp is only myth
RA has adapted all big and major scenarios and campaigns. Currently we are waiting for new update of RSR campaign because RA developer found there some bugs.