The LE is out of stock.
The SD has a SF muzzle device that accepts cans.
The SD has the Nano coating on the muzzle device and BCG.
The SD has a nicer more functional handguard.
The SD has a Geissele trigger which is generally nicer than the ALG trigger.
The SD is available in 4 color options.
The SD comes with a nicer stock.
For me there would be no question.