The funny thing I've noticed with my hoggie, I can see her little red eyes watching me move and tracking things. You can watch her watching you, so when my other hand moves she tracks it, unlike the BPs who are completely oblivious until you touch them and then they "jump" with surprise, forget you're there after 10 seconds, and get startled again. I have seen the hogs doing the "no really I'm dead" roll over on youtube, but mine doesn't do it. I think she's just lazy or defective (or hopefully I just don't scare her).
Since my only recent experience (I had a burm, hoggies, and a corn as kid, which was an undisclosed length of time ago, so I don't really remember how "smart" they were) is hoggies and BPs, I vote hoggies as mildly smarter, but it's not like the bar is set very high.