I read some articles about mixing tapes.... basically Panasonic have about 70% of the market share, Sony has 20% and TDK has 5%... However many other brands use Panasonic tapes and rebadge them... (Canon and JVC for example)
There is an idea that mixing different brands may be bad for video recorders / camcorders because the lubricants used differ from one make to another, possibly causing problems.
Article Here
I know that when my company used to service video recorders, we could usually tell who mixed video tape brands and who stuck with one or two brands.... tape deposits (fine black dust) were more evident on machines where many various brands were used. Scotch tapes used to shed a lot of material for some reason.
Anyhow..I'd stick to one brand of DV tapes seeing as the little video head drum works so hard.....no point making matters worse.