Save as ProRes 422 format always instead of H264?

My head is about to explode...this seems like it should be such a simple question. I've been reading for seemingly hours and don't feel like I've made any progress! :-O

So situation is I have a number of movies as MTS files (originally taken from a Sony DSC-RX100 camera); all relatively short in length, never really longer than a few minutes. I normally use iMovie, but on occasion play with FCP also.

I have been reading about lots and lots of MTS converters (free and paid), and regardless of what app I use, I am mostly wondering what format I SHOULD be converting these into in order to have a file that is high-quality and flexible for relatively basic future use? And then I don't want to keep tons of basically unnecessary files, so I would prefer to convert to a "usable" format and then get rid of the MTS files assuming I don't need them.

The H.264 file format (of those below) actually looked the best to me after importing all the different files into iMove to take a look (though the others all produced an initial error message, though upon reopening iMovie could be viewed).

To play around, I converted a 200MB MTS file into a 110MB MOV (H.264 file) file using Xilisoft HD Video Converter, and into a ~1.6GB ProRes 422 file and ~900MG AIC file using Clipwrap (both produced errors for some reason, but did import). I also tried converting into a MOV file using Total Video Converter Lite, though iMove produced terrible quality video... I tried some other formats than the above but there were artifacts galore...

Anyway, I'm sure this has been asked a zillion times, though when I read here it seems to be folks looking to do more advanced editing than me...

There needs to be a "video file format for dummies book"

"If you are a basic user and need to convert your MTS files, just conver them to _____ and stop thinking about it..."

Thanks all!