Been involved in DClin shortlisting for several years and it tends to be the least important variable on the form. While the form does show your degree class and university, there is way more on the form that gets you selected for interview. The nearest to that I have come across some selectors look for individual module marks, particularly in research methods.
Must have sifted through about 600+ forms in my time, and there has never been two identical forms where undergrad degree has been the only differentiating factor. In fact if that was to happen, I may even rate the candidate from the lower classified university more, as it would demonstrate they have 'come further' than the one at the more prestigious institution to get to exactly the same level of experience and reflection (like they do with contextual offers). But that's just me.