What's the point of clipwrap? There seems to be little to non what clipwrap can do and FCP don't. Clipwrap simply "unwraps" mts files but the resulting MPEG files can't be edited in FCP without being transcoded in ApplePro Res, AIC or other editable codecs. However, this can be done with FCP directly as well.
FCP can't import .MTS files directly without them being a part of a structured file system. By wrapping them in a MOV wrapper, you can manipulate the files directly by anything that understands QT (e.g. FCP, Compressor, QT Pro, MPEG Streamclip etc).
On the other hand Premiere Pro CS5 (and even it's offspring Premiere Elements 9 for Mac) can handle AVCHD files directly in it's timeline with no need to transcode at all before it comes to distribution (Blu-ray, h.264,...).
While there mightn't be transcoding, there will be rendering. If you choose to cut, colour correct and perform other transformations directly on AVCHD files in the timeline, there will be a penalty to pay both in quality (multiple renders on sections of an AVCHD file may result in obvious compression differences between that section and bits that haven't been altered) motion graphics won't be as smooth as they could be, colours could be out as you keep rendering in 4:2:0 and you could be rendering more often as the sequence gets more complex.
If you don't expect to have complex sequences or colour critical needs, and you just want to get in and start cutting MTS files, then Premiere (pro or elements) is a fine choice. It does very well. This isn't a FCP versus the World thread, it's about selecting the right tool for the job and getting the most out of it.
I use FCP mainly with DV so I don't even get into ProRes, but I use FCE with AVCHD files, transcoding into AIC. On a C2D iMac I can lay 5 simultaneous video streams in a timeline from the internal drive and playback all in full quality without dropping a frame, so that's pretty cool. That Adobe CUDA thing, that's pretty cool too. In this game, what is "best" is a moving target. I remember CS4 coming out with the ability to edit AVCHD directly and it had (has) some very high system requirements. But what does Panasonic say: "While it is true that CS4 reads and edits native AVCHD files, editing a long group of pictures (GoP) MPEG-4 format can be somewhat tedious. And in fact, AVCHD as a format, was created as a high quality, bandwidth efficient
camcorder codec."
It'd be handy if iMovie could edit MTS files directly, but remember that Apple was the first to give consumers real editing of AVCHD, and even now iMovie will edit AVCHD files (transcoded) on a 4 year old iMac: plug in camcorder, select clips, import, edit, share. Consumers don't really care about transcoding (really) and following the simple "plug camcorder in" workflow, they'll never see an MTS file. They just want something to work.