Not much difference, I'd say: the HIP might be produced earlier than the searches would normally be carried out, but the sort of stuff that's revealed doesn't normally change rapidly, and the buyer should be alert for new planning applications and so in any case. In the old "Requisitions on Title" which the buyer raised between exchange and completion (if his solicitor could be bothered) there was normally a question about whether the answers to Enquiries before Contract had changed. I'll see whether something similar is asked about the HIP in a few weeks, perhaps.
But yes, I agree: HIPS would be fine with some tweaks to the forms and removal of the green nonsense.