Those 20 gigs give me uncompressed PCM 7.1 audio on shorter films and room for lossless Dolby TrueHD or DTS-HD MA on longer films where PCM won't fit. Totally worth the extra space.
BD+ doesn't disable players. I've seen you post this before, and it's simply not correct. BD+ launches a virtual machine inside the playback device that ensures secure communication between the disc and the player. Should the security in the playback device become compromised, the device manufacturer shares its security key with disc authors, who enable a workaround on the disc that allows secure playback for future titles despite the hack. It does not disable playback in any way. Discs issued before and after the hack will continue to work as expected; BD+ merely provides a way for content authors to secure new releases after a player has been compromised. This won't help older releases, but it protects new releases.