Trying to be a bit more durable than most LBX10 builds by mounting an LE. RLs are nice burst damage for very little tonnage dedication.
Very heat efficient, so could always switch to ERMediums. I do think RLs are a nice addition to the game for old medium 'Mechs like this, which often had more hardpoints than their tonnage could use.
ERML are possible, but have lower DPS too. It's whatever you prefer (could even go to MPL if you really want)