My understanding: Gephi doesn't do well with real-time updates; it's usually used on static data.
One major consideration - what is the visualization you wish to present? Is it a directed graph? Cyclic? Weighted? Additional labels?
Some toolkits are 'fixed' in what they can display, but make it easy to present a graph. Others (like d3) are very extensible, so you could create just about anything.
For the purposes of the StackOverflow format, you might get better answers if you can pin down the limitations and needs of your system (actual data rate, thin/thick client, type of viz, etc)