The preference must depend on usage.
The lithium AAs hold several times more charge than any AA rechargeable technology.
They are also 1.8V so have an extra margin before the camera decides they are flat (which happens ~ 1.2V). I did use 1.5V alkalines but they are "declared" flat pretty fast (incorrectly), and 1.2V NIMH cells work for about 5 minutes...
I find the lithium AAs last long enough to fill up a 4GB SD card i.e. about 1000 shots and they cost (UK) about USD 12 for four. Of course, if you shoot 1000 pics in a day then this
is a major issue - but then you will be carrying a backpack with some precharged batteries anyway. For me, the 1000 shots is one long (2 weeks) holiday, with loads of aerial shots (from a light aircraft) plus maybe 6 months back home. And the thing which really matters to me is that I have never been caught with them suddenly flat, whereas this happens regularly with LI or LIPO rechargeables which go flat at the worst moment. They also have a poor shelf life, whereas lithiums last for years.
IMHO it is a basic principle that you never know for sure when batteries will go flat. With rechargeable ones, you have to carry a spare, and with non-rechargeable ones you also have to carry a spare. Except that with a AA-camera you don't have to carry anything because you can buy them locally, and the shelf life of the lithium AAs is at least 10 years. They are also small and very light.
Maybe the Pentax K-7 batts are really exceptional but I have never seen a LIPO battery which held its charge for more than a month or two, which means that when going away for any time one needs to carry not just a spare battery but also the charger, and here in Europe that is extra hassle. I am trying hard to avoid carrying a whole bag of chargers