PS3 True Blue,PS3 Cobra Dongle as well as PS3 E3Flasher,just as the title suggested,they are the PS3 USB dongle used on your ps3.Maybe most users have known them better,so,following just a simple summary about the relationship between them.
First let us look at their mainly function by simple words :
PS3 True Blue is another PS3 USB dongle
which used for jailbreaking your V3.55 PS3 and playing V3.55 to V3.73
games which require V3.55 higher system,by which you can play any V3.55+ PS3 games on your PS3 V3.55 system.
With Cobra USB Dongle,you enable to run Blu-ray, DVD and PS1 game iSOs
and PSP Mini games from your PlayStation 3 hard drive on your ps3 firmware v3.55.
E3 Flasher
you can use this item to downgrade your V4.11 PS3 to V3.55.It is a
special device to help you programme NAND and NOR flash data. It is
upgradable via a TF/SD card. According to info from official team, this
item can support all electronic devices including
DVD/BD/PS3/WII/XBOX360/MP3/MP4/Table PC which has Nand or Nor flash
memory.
In all,no matter which items you want to use on your ps3,you should keep your ps3 firmware was v3.55.That's to say,both of these three dongle can just run on ps3 v3.55.
Summary
1.If you ps3 firmware was v3.55 or lower,you dont need buy anything to play v3.;55 or below ps3 games.If you want play v3.55 above games,then you need buy a ps3 true blue,by which you wan play any V3.55+ PS3 games on your PS3 V3.55 system.Or you can buy cobra to enjoy more function,such as running Blu-ray, DVD and PS1 game iSOs
and PSP Mini games from your PlayStation 3 hard drive on your ps3 firmware v3.55.
2.If your ps3 firmware was v3.56 or higher,then you need use E3Flasher to downgrade your ps3 firmware to v3.55,then you can paly v3.55 or lower version ps3 games. Then with a ps3 true blue,by which you wan play any V3.55+ PS3 games on your PS3 V3.55 system.Or you can buy cobra to enjoy more function,such as running Blu-ray, DVD and PS1 game iSOs
and PSP Mini games from your PlayStation 3 hard drive on your ps3 firmware v3.55.