I haven't tried LogMeIn Ignition, but I did recently purchase Splashtop Remote. I have no basis for comparison, but I am pleased with the $2.99 I spent on it. I agree that the controls are a little convoluted, but for the simple tapping that I do when using it, the controls suffice. I can't figure out how to make my auto-hidden dock appear when I try to hover, nor have I really mastered hovering at all - but again, for 95% of my use of Splashtop, all I do is click anyway.
The sound is good, the video is good also. And I, like many others on this thread, have configured it to be able to be accessed over 3G, so no complaints there. It's really not difficult.