Originally posted by geomez I would say only keep two systems if the Nikon offers something that you need or frequently use that the Pentax does not have. Otherwise sell it and put the money towards glass.
Agreed.
If your main concern is the "Bad weather photography" Pentax is the way to go. Both cameras are great, but at this stage I don't know if there is a real reason to expand both. See which one has a better upgrade path for you with lenses and features you could honestly see yourself using and go that route.
Pentax's pros:
Small, lightweight, weather sealed, high quality build on the bodies
Limited lens series is small and very good optically.
good selection of excellent prime lenses (FA Limiteds!)
value for the money is usually very high
image sensors have unreal dynamic range (useful in RAW edits)
Pentaxforums community is pretty awesome
All bodies support screw drive auto-focus lenses (your Nikon may not)
Pentax cons:
limited amount of after-market glass available
limited dealer stock/support
many items are special order depending on your dealer
no 35mm upgrade path available
auto-focus is arguably not as good as the competition