What settings for a new master file (combining several source files)

Hi,

First time user of Premiere CS6; I am just getting started editing holiday AVCHD videos, and have a probably easy question for those who are a bit more well-versed than me in Premiere's preset/settings.

• Let's say I have three AVCHD source clips on the same theme.
• I create a project using a preset that match the source files from the camera (Sony Nex-6) and import my three sources using the media browser.
• I edit them together with titles and transitions.
• I now want to create a new master file for my own viewing pleasure, that matches the quality of my sources, so I can throw away the 3 sources and only keep the new, edited "master source". (After that I will export in various web formats for vimeo etc).

I have read here on the forum that I should not use "Match sequence settings", though I don't understand the technical explantions offered as to why.

So, given that I want to avoid re-encoding, and have a non-lossy creation - how should I create my new, edited master source?

EDIT: My sources are 1920x1080, progressive, 50 frames/sec, H264 MPEG-4 AVC (part10) (h264). I only seem to be able to export at 25fps using the MPEG2 Bluray format (which in my understanding matches my source files from the NEX6 at it's highest AVCHD quality)