Need help in choosing right Bluetooth Module among these two.

Hii arduino lovers. ;) I want to buy a new bluetooth module to drive my arduino Robot from PC or mobile(will develop an app soon) etc.. After a lot of research I am struck to choose one of these. The thing I am struck up at is the difference between these two modules,: one is bare HC-05 bluetooth module and the other one having an extra PCB soldered and attached to the lower side of HC-05. AND

what are the exact difference between these two boards and IF I can use the bare HC-05 module to interface directly with arduino( then why there is need to have other one..?? I wanted to know the exact technical difference between these two modules and which one I should go for and which one would be more advantageous..?? Please help with issue I am new to bluetooth protocols... :relaxed:

The extra pcb has a voltage regulator. So that one is for 3.3 to 5V. It wouldn't help much, since the digital signals are not 5V tolerant.

If the small board is soldered to a pcb of your own, you might as well use that. But if you plan to solder wires to the small board yourself.... Well, I tried it once, and that was the last time I will try to solder such connections.

@edrin: thnks.. ;) so basically not much difference between the two boards except the voltage at which they operate.. I don't think I would have problem regarding its small size.