It's important to remember that while invisible, you can and will still be attacked. When a face attacks, it simply selects a random enemy vertex next to it, making no distinction between occupied and vacant vertices. This means that you can reduce the likelihood of a face attacking you by capturing some other vertices next to it; often a useful trick to know. But it also means that being invisible provides no advantage against enemy faces. Obviously you do get an advantage against enemy players, because they don't know exactly where you are, but still they can often figure it out if they're paying attention. Robots are affected, which makes quite a difference when you're dealing with Shield Robots, which need to know where you are in order to block your attacks. And of course Hunterseekers can't home in on you and Laser Turrets can't attack you if you're invisible.
In a way, I kind of think Mighty Vision is better than Invisibility, because the amount of extra information you get is more than the amount of information Invisibility hides from your opponents, especially since Mighty Vision lasts considerably longer. But Invisibility's a lot easier to use, and the advantage it gives you against Shield Robots and Laser Turrets makes it indispensible.