Hi John, for interviews to be interesting at the show, I think you'd have to invite the manufacturers prior to the show. Ideally the head person from each company, or head of their regional office, would be interviewed so as to maximise the chance of quality information. It would help to get a peak at their booth prior to the interview so you would know what camera angles would be best and how many products might be discussed and shown. It's a fair amount of work scheduling a bunch of interviews at a show but I do think it helps to pick up on the atmosphere of the show, be it good or bad.
While I do like your webinar idea, I see a few possible negatives. At a show, you could probably do quite a few 5 minute interviews whereas you probably wouldn't manage as many webinars as they tend to be much longer, perhaps 30-60 minutes each.
Furthermore, webinars run the risk of becoming beat-up-the-manufacturer events and you might find manufacturers are unwilling to participate.
Interviews at a show are probably less threatening and more likely to receive cooperation from manufacturers. IPVM members would then have a chance to discuss the interview afterwards and of course manufacturers could respond to those posts if they so wished.
Given you have previously tried interviews at a show, maybe you could trial webinars and see which works out the best? Thank you for considering my request.