AC-powered vs. Bus-powered external HD: Media file playback performance via USB?

[ToddGack]

I store all my video content as .mkv or .mp4 files on external HDs. I plug these HDs in to my Blu Ray player which has a USB port, which is connected to my TV with an HDMI and that's how I watch the files on my LCD TV. Up until now, I have been using Bus-powered external drives (like the WD 2TB Passport for example) and the media file playback has been..fine. It's time to get more storage, however, and I'm wondering if I should consider getting an external drive with a separate AC power source? I'm aware of the usual pros and cons for AC-powered vs. Bus-powered external HDs, but I can't seem to find a definitive answer as to whether or not the AC-powered drives will make any difference in the performance/playback of my media files when the drive is connected via USB through my Blu Ray player to my LCD TV? If there isn't any difference, I'd just assume get a Bus-powered drive for the portability factor. But, if there is a difference, I'd like to get the best possible option..and plugging the HD to a power source is not that big of a hassle. Any input would be much appreciated. Thanks.