The way my ignition is set up it gets its crank timing well, from the crank. This allows for the timing to be much more solid. In a stock honda setup, you will notice that the timing bounces around a little bit. This is due to it getting it's timing signal from the opposite end of the crank which is not the most acurate being that it has to go threw the timing belt which will cause it to jump around alittle. This is also a very redible ignition source at any junk yard that also has the ability to go 10,000 plus RPM and multisparks at idle up to 3k rpm giving it a much better idle. 3rd, the EDIS controller handles the advance and not the ECU taking off some of the processing overhead from the ECU allowing it to focus on other things.
As far as why it is better. I think in the long run, it is a little cheaper then chrome if you tend to change things a lot like I do. Sure, Chrome is free, but if you want RTP, you need to get Chrome Pro $150, Ostritch $100. We are now at the price of the megasquirt. Now, what about traction control... not launch control, traction control. Megasquirt gives you the option to monitor rear and front wheel speeds, and when they are different it will retard the timing until they are the same. Along with traction control, boost control, nitrous contorl... The list goes on. I have not done real time with chrome yet, but it is my impretion that you have to do a run, burn the change to the ostritch. do it again... With MS, when you make the change, it is live then, no reburning. You can make changes and watch the effect in real time.
Dont get me wrong, I dont have any issues with chrome. I currently run it in my boosted del sol, but I just prefer the MS.