When you gate check on an RJ you will have to wait on the jetway at LAX to receive your gate check item back and have all of your bags to carry on LAX-EWR. Gate Check Bags are unloaded at LAX on a Last in First Out basis so there is no Elite treatment of Gate Checked bags. During short connections sometimes it is better to just check your bags through but with 1.5 hrs you should have the time to claim your gate checked bag and make it to the next gate.