The diffrence's Here is a quick run down.
5hz's has allot more channels vs the 11 2.4hz's has
Which would elimiate more of the cross channel noise.
5hz's is also a higher frequensee so you have less apliances around you house that create noise like microwaves and what not.
At the same time since 5hz's is a higher frequense it does not pass throug objects as well as 2.4hz's
real world senrio.
My home network with 3 appletv's work alot better runing HD movies over 5hz's because there is less noise on that channel
At 2.4hz i do not get as solid of a bar but i could go across the street into the yard and still have signal.
At 2.4hz i get a solid bar to the other side of my yard and my whole house first and secound floor.
My current setup is 3 wifi setups because of the mixture of devices i have.
first is G (uverse gateway) used for old Iphones (i have 3 in the house)
then i have a apple extreme router setup with 2 N's 2.4 and 5 appletv' in house either wired or setup for 5hz's and laptops'
2.4 is for my 3gs iphone and if i ever need the reach.