Having a Mechanical TCSA is an advantage over an electronic advance in so much as you can tune your spark curve. You can bring any amount of advance in at any RPM you so desire to tune the idle, midrange and top end timing. But, if the electronic advance is perfect for your setup than you can't get any better than that...

Electronic:
Pro;
No moving parts
Can move the total advance 'window' (usually 26 degrees) up or down a few degrees.
Con;
Can't control the timing curve or total timing. Not very tunable.

TCSA:
Pro;
Totally adjustable timing for total advance and the curve at which it comes in. Tuneable.
Con;
Moving parts, they don't really wear out but can get bent or bumped if hit hard enough.

That's how I see it. Again, if the electronic ingnition were set up properly for a given motor and flying type then that would be my choice due to simplicity and that you can't get any better than perfect once it's right. If you are a serious gear-head than go with the TCSA.