Tablets are definitely more portable, but our experiences have shown that indeed, sales people do still make presentations off of laptops - 100% of the time. I think the tablets mostly suffer from a good interface to the (ugh) VGA connections of most projectors that are used in conference rooms. In addition, the fact that laptops are easier and have no cost to connect to corporate networks, combined with the built in HDMI ports in almost every laptop, means that even if there is a big flat screen in the conference room, I don't need special connectors to tie into the existing equipment.
I am actually shocked to see how few sales reps actually have tablets. We have even seen one or two that have tablets, but bring their presentation on a thumb drive, to be used on our equpment. Sadly, our sales force is no different - we give laptops to managers and sales people rather than tablets. I think that smartphones and tablets suffer from the same issue - you need to carry special connectors for connecting to conference room equipment. Also, it's just easier to use the same device that you do your work on to present with.
Tablets are great for playing games and doing social media, but it's hard to get any real work done on them. I love typing on my iPad2, but 90% of the people I talk to find it tedious and troubling for work documents. I have tried to find use cases at work for some to justify a purchase and testing, but I just cannot find any.