It would be worth checking the DVD-RAM & DVD-RW feature comparison table on pages 8 & 9 of the manual for the Panasonic DMREH50. This manual can be downloaded from Panasonic’s online website operating manual section.
Going by the manual of the product, the main advantages I see with DVD-RAM over DVD-RW include the following:
[li]Slightly faster HDD -> DVD burning of 5x (DVD-RW = 4x)
[/li][li]Ability to play back a recording that is currently taking place
[/li][li]Record Multi-channel TV Sound broadcasts (MTS + SAP)
[/li][li]Record 16:9 natively (DVD-RW converts to 4:3)
[/li][li]Disc does not require finalising to play on another DVD-RAM compatible player
[/li][li]Record broadcast flag protected programming if the flag allows one copy to be made (requires CPRM DVD-RAM media)
[/li][li]Recover space by deleting titles (DVD-RW must be erased to recover space)
While this does not mean that the LG-RH7500 will have the same limitations as the DMREH50 for DVD-RW media, it should give an idea of some of the differences.
DVD-RAM does have a drawback in that only DVD-RAM compatible DVD players and recorders can playback this media. To access the disc in a PC, you will also need a DVD-RAM compatible DVD-ROM or writer.