I suppose when you are talking about enlargements past 16x20 or so I am a "die hard" 6x7 MF and LF fan.
I don't think it's helpful to be a diehard on any issue. It's better to have an open mind. Of course MF and LF is more suitable for the big enlargements. But when you examine the reasons for this, the extra detail is surprisingly not always the major factor.
I believe studies or polls on this issue have shown that the significant and very noticeable lack of grain of the MF enlargement, plus the greater tonality, often counts for more than the extra detail.
In other words, if it were possible to remove the grain from a 35mm film without sacrificing detail and also somehow impart greater tonality to the image (more subtle transitions from one shade to the other), a 24x36 enlargement from that 35mm film would generally be preferred to the same size enlargement of the same scene from an MF film which had had grain artificially added to simulate 35mm
Now, when it comes to enlarging digital images, the best of the DSLRs are essentially grain/noise free. In fact, I wouldn't be surprised if a 24"x30" enlargement from the tiny 22mmx15mm D60 sensor showed less grain (in areas that are supposed to be 'clean', such as the sky) than the same size enlargement from 4x5 film. So, in effect, a good digital camera already has built in, one of the major factors why MF is preferred for big enlargements.
Now, don't get me wrong. I'm not trying to disparage the larger format. For any enlargement that relies upon fine detail for its major impact (and that's almost an oxymoron), the larger the camera format the better.