closed loop could in theory give worse fuel economy, as you could map it to run slightly on the lean side for fuel economy whereas closed loop will correct it to lamdda = 1 (but you would not want to map it lean as the torque would be lower, temperature higher and so on).

a good chip will be very nearly as good as closed loop, but obviously closed loop has the ability to make fine adjustments to keep the mixture constantly correct (under the running conditions that allow closed loop operation of course).

if you can either afford the option of only closed loop fuelling or wasted spark coilpack, i would go for the wasted spark everytime as the fuelling will be very good anyway, and the wasted spark gets the best from the fuelling and gives benefits over the whole engine operating range from idle to full boost.