Which is better? Mpeg4 or AVCHD

[Deer Film]

No matter what Canon camera you will get, it seems you will have the option to film in either Mp4 or AVCHD. Having owned the Panasonic HMC-150 and a different Canon Vixia, I am so used to filming and editing in AVCHD. Never had a problem with my computer set up and I use Sony Vegas, and Affter Effects.
I had a person tell me on my youtube channel that Mpeg4 is better quality and easier to work with. I know the Mpeg 4 offers slow mo. I thought Mpeg4 for is more compressed file format then the AVCHD.
Could someone give me so more technical reasons or to re-confirm that Mpeg4 is the way to film and not use AVCHD. Or do they have their own strengths and weaknesses.
I am after best quality. Thanks for your help.

 

[Bassman2003]

Testing is going to be the only way to know this. At the core, both are the same animal as AVCHD is a variation of h.264. Bitrate plays an important factor here but bitrate alone does not ensure quality. The coding of the mp4 compression is very important. We do not know how good the mp4 implementation from Canon is until it is tested side by side with AVCHD. It might be a wash. The mp4 at 35mbps has a decent bitrate. Hopefully the codec will be efficient to at least equal AVCHD.