I was wondering, if anybody could please tell me the major differences between Driod and HTC in the perspectives of their credibility?
Droid is actually a product lineup of Android phones from Verizon Wireless. HTC is a device manufacturer.
The Droid lineup contains devices made by both HTC and Motorola.
HTC is well known in the world of smartphones, as a matter of fact I believe that is all they make. As for Motorola, they are the oldest name in the cellphone business. I believe the first cellphones were Motorola devices, Moto is also a big name in communications radios.
Moto's credibility was going down the tubes up until they launched the original Motorola Droid. The Droid was a superb phone, and was extremely open as far as modding goes. The newer Motorola Droids (Droid X, Droid 2, Droid Pro) have encrypted bootloaders and run the Moto Blur interface, so they are a bit harder (although not impossible) to mod. Build quality, however, is quite good.
In the end, I don't think you can go wrong with either manufacturer, it's more a case of spending some time in-store with each device and seeing which one is a better fit for your needs.