It really comes down to workflow.
Now, the mp4 format you are getting from your camera is NOT raw. It is a highly compressed datastream that contains a lot of information. Raw video footage tends to be extremely large and you need a very fast system to process them. These compressed files allow a wider variety of programs to access the footage.
Now, an important thing to realize is that editing video and playing video are very different processes, and video files that are easily played are not necessarily easily edited. Premiere tries to take some of the workload off of your shoulders, but you still have to be mindful of the fact that these files you are getting from your camera are not necessarily easy for your computer to edit.
That being said, the destination of your footage is very important. Are your movies going to be sent out as video packages for laymen to view on their computer? Then you need a good easily translatable file that is compressed enough that the file sizes will allow for easy distribution and playback. I recommend H.264 with one of our presets - They will cover most needs.
Are these movies going to be held onto for awhile on your computer to be used in another program or even brought back into Premiere for further use? If that is the case, then you can try to match the settings of your original footage as much as possible - using H.264. It's not going to match exactly, as the files are not being used for the same thing - storage on a camera vs editing in a NLE.
There are some good intermediate codecs available that are not part of Premiere but should work. I've heard a lot of chatter on here for DNxHD and UT. Both of those are free.
Shouldnt there be a function that when you import a video you can keep the raw files exact settings?
It's actually quite rare in the world of professional editing, the market PP is aimed towards, for the end result to be in the exact same format as the original. That would definitely be more of a 'consumer' feature, so if it's important to you, you may want to look at consumer editors.
The movies I am recording arent coming from a camera rather from a program on my computer called Xsplit. They are stored on my HD and then edited to be uploaded onto youtube, Im not sure if that makes a difference or not to what you said earlier. Thanks for the reply