I have hit a couple of issues now I have seriously started streaming from my HDR- to my HD-FOX. StDef is absolutely fine, and in general I record in StDef for maximum versatility (and economy of file size).
Some things however are worth watching in HiDef, and two recent experiences are one recording bombing out (repeatedly) at about 56 minutes, and another one having non-repeatable sound stutters and sound loss. I need to check they play properly at the HDR-, and then perhaps try transporting them to the HD- by USB.