What do IB folks think of Corp dev folks?

Corp Dev is more closely aligned with PE than IB. Corp Dev is the internal buy-side aspect of a company, and they are the ones that evaluate deals internally the same way a PE associate would evaluate new investments. Not really sure you mean the work isn't different unless you also think that PE is similar to IB too. 

I've worked in MM PE and Corp Dev at a F300 company and I can tell you that the general internal sentiment is that the bankers always use unrealistic models because they are trying to get deals to transact whether it's a good investment or not since that's how they make their money. IB work isn't necessarily hard or impactful when 75% of the deck isn't even scrutinized (not saying people won't look at it, but no one is going to tell that a logo was resized, or the color scheme was off by 1 shade on page 75 compared to page 32) and the models that are provided are largely rose-tinted and not in line with realistic performances. I'm sure bankers will have negative opinions about Corp Dev and PE clients as well (probably relating to time crunches and making bankers fit their schedules).