J.J.
I have had all of the above... My first home was a ranch with all the bedrooms together - we only lived there until my baby was 7 weeks... my next 2 homes were both 2 story and had split master down, other bedrooms up -which had its pros and cons - the house had a very open floorplan - so even though the kids were up - it was noisey!! We also had a 2- story with all the bedrooms up - it was fine. Then we had a 2 story (actually 4 with full basement and walk up attic) - where the kids bedrooms were all up and again the master was down, and now we are in a ranch with split bedrooms.
This is my favorite house - it is 4,000 sf on one level - so the kids rooms (3 bedrooms and 2 bathrooms) are all on the opposite side of the house from the master - which is great b/c they are all schoolage now. The kitchen is on the opposite side of the kids rooms - and this house is quiet - I don't hear the t.v. from the family room from my bedroom - it does have an intercom system as well... I don't miss the stairs!! I love the look of a 2 story - but after doing my last house - I am done with them!!
Find a house you love - ultimately it doesn't make that big a difference!! My kids can easily get to me in the night if they need me!