Using a programable EFI computer to control the timing gives you complete adjustability and fine control (so you can tailor the ignition for best power & driveability) plus being able to use hardware that will give you a great spark. There is no need to regularly adjust the system or replace bits as it wears (like you do with points). The benefits are better power, driveability, reliability, economy and easier starting.
Using a crank trigger ignition removes the mechanical distributor drive components from the ignition system and improves the timing accuracy (Nice if you ever use high revs and/or boost).
As I said, if you use a programable EFI computer you can also use it to drive fuel injection or even water injection. I don't know what your current inlet manifold setup is but replacing it or converting it so you can run injectors will yield big improvements in power, driveability, reliability, economy and easier starting and will allow you to use an intercooler so you can safely use more boost and get even more power (which is why you're turbocharging in the first place, right?). Water injection can be great too, but I don't want to be typing all night so I'll leave that for now.
The downside of programable EFI is cost and complexity, especially on a car that didn't have it stock.
Since you seem to have the confidence to tackle a Cordia ignition unit & knock sensor transplant you might find assembling a Megasquirt (
http://www.megasquirt.info/ ) to be a cheap way to get an excellent EFI computer. I don't know what the current pricing is and it depends what version and specification you want but we're talking in hundreds, not thousands. I'm using one with 4 LS2 Chev coils (EBay, about $140 landed here), a knock sensor (from the wrecker) and I've just made the crank trigger components.
The fuel side requires at least one EFI fuel pump (plus wiring, a relay & I recommend an LPG safety switch) and a filter, possibly a swirl pot, definitely new rubber fuel lines, a fuel rail and regulator, a return line and injectors. Price depends on what bits you choose, new or second hand and how much you do yourself. Or you might consider going straight LPG and the government'll kick in $1500 bucks (I think that's still current) to help with the conversion. There's carb and injection options there, too depending what you want to spend (but blow-through carb is the cheapest that allows you to run an intercooler).
And you'll want an intercooler.
Whatever you choose, allow money and time for tuning. This is critical! I'd expect LPG carb to be cheapest to tune, followed by EFI and then suck through petrol carby with custom distributor based on the amount of time and fiddling required.
I wish there was an easy "rough cost" I could give you but it all depends on what parts you choose and how much you do yourself. Some research will be needed to find the right answer for you.
Enjoy!