There's really just too many factors to give any sort of reasonable answer without exact specs for each drive. My gut feel is with most cheap / slow drives able to go above 20MB/s (think a large RAW every second) you won't really see much difference either way.
Somehow that is my feeling too. Though I don't have experience that can confirm that I not really will notice. I wish to be sure that it does not become slower as with me previous Notebook. That would be a real bummer.