it's all about what you like and you can get the circulation to the point you have no dead spots, I had a 37g tank set up like that but I made sure to have a few caves for the fish , and gives area for water to move with in the rock
the one thing I did find with the whole tank full with rocks was the circulation never got every part of the tank , another thing was there was less areas to put corals since everything overlapped , I just happen to get lucky with this tank that I had placement for lots of coral , but my swimming space was limited I loved this tank as it turned out nice ,
I had many tanks when I was young, but this was my first tank I started after 20+ plus years of not having one , than I up graded to a 40b and went with the split layout I found the fish seemed more content having more room to swim , I also found the split lay out helps cut the aggression with the fish as they each have there own territory , you can have more caves for the fish , and it also gives the inverts more places to Rome , it also helps give you more places to put coral as you can place more ledges and such this way you can keep
sps on one side
lps on the other than fill in all the blanks with zoa's and such
this is another tank I had the 40B as you can see you can get a more natural environment that the fish seem to enjoy
than after I tore this tank down I went to the 90g and I'm still working on getting to look like my old 40B
if you see in this pict with the split layout you can sit your rocks a bit differently giving more flat surface area for corals as you can sit rock on a angle giving more room
take your time till your happy with what you have and your tank to will come alive