5 GHz, as you might imagine, is a higher frequency that will support higher bandwidth.
There are very few 5 GHz networks in operation, so there is minimal chance of interference with other networks....almost all which are 2.4 GHz. That will change as just about all new routers being introduced are dual band 2.4 GHz and 5 GHz devices.
But, everything has a downside, and the rub with 5 GHz is that the higher frequency signals are weaker than 2.4 GHz signals, and do not penetrate walls, ceilings or other obstructions as well as 2.4 GHz.
If you have line of sight between your computer and the wireless router, 5 GHz will provide a faster connection with higher bandwidth capability.
If the wireless signal must pass through a wall or two, 2.4 GHz will probably provide a stronger connection, but it will not be as fast as 5 GHz and there is much greater likelihood of interference issues from other nearby wireless networks. Most cordless phones use the 2.4 GHz frequency as well, so that complicates the potential interference issues.