Most of the major components inside the ALX R1 is upated like the motherboard, cpu, gpu and memory cards. Basically most of the major parts inside the Aurora ALX R4 is updated including the 4 HDD/SSD storage drive caddy is updated in the R4 I believe the newer drive bays are easy to install, that's if you ever want to swap HDD/SSD, all you have to do is just pull out the drive bay and slide the new drives back in. Unlike the R1 you would have to unplug the wires first then slide the drives out and vise versa. Not much of a problem, but it's an added hassle free addition to swapping drives if you ever needed to.
Other then that I believe that's it all the other features are identically the same as the R1 (ex. LED interior lighting, ALX Gimmicky fins all remain the same including EFX lighting).
If you want you can google and look up interior pictures of the Aurora ALX R1 and pictures of ALX R4 and do a comparison of the 2.