I am making one big assumption here that the OP will be looking to buy more lenses and upgrade at some point so if the deal hasn't already been done I'd suggest the OP considers this decision as a choice between systems. I mean by this that the OP will be choosing between a system of cameras, lenses and accessories like flashes, remote releases etc and on that basis it's worth looking at the wider system now even if you are only looking at the first investment in the system.
The general questions I'd ask myself in making the choice are:
1) How available are new original maker system accessories (Nikon or Pentax batteries, lenses, grips, flashes etc)
2) How available are new third party system accessories (batteries, lenses, grips, flashes etc), these are generally cheaper ways to get more kit
3) How available are
second hand accessories (both original maker and third party)
4) Can I hire accessories for a one off events
5) What do my other people I know have and do they have things I can borrow (on TP meets I've been on there is a general lending culture going on, so you can get to try a huge range of kit if other people have the same the system as you)
6) Is there a future for the system I'm choosing? Hard to assess but in general I mean what is the risk of the original makers stopping making SLRs which will make the availability of kit drop or are they making a big investment and the availability of kit is currently rising?
Looking at all of these I would put Nikon on top of Pentax but of the two models you've listed I'd put the Pentax slightly ahead of the Nikon. You have to look at whether you want long term benefit of a wider system and cheaper total cost of ownership (Nikon) vs a short term better first camera (Pentax).