Sony A65 or Nikon D5100

I plan to leave my 5 year old FZ Pana in favor of a DSLR. I would also add a prime lens and a Tele lens.
I take nature shots, outdoor scene & some portrait

I wish to improve on my current image quality and also play with post imaging software.

Which would be the best choice....limited budget a consideration....Sony or Nikon????

Thanks
Bernie