In my opion and experience with A-series and now a CA, you have to look at two things;
1- How much cash flow you have at your disposal,
2- What you intend to use it for.

A-series is a great, don't get me wrong and makes an unreal street car for everyday driving, while,
CA18det is alot of hassel, all the things that have to be modified(brakes, diff etc) i think is more suited to a race application.
They both are an exellent choice for a race application, but i prefer putting my CA coupe on the race track due simply to the fact that you can't drive it to its full potential on the road, After all it is a serious performance modifacation and it should be driven too it limits(And your own limits)
driving on a race track is an entirely different beast all together,If you think your a great driver on the road, unless your car is set up right you will have difficulty being compeditive, and that takes time and money, Its great i love it!

so............................................
IN MY OPINION, I would use an A-series for a street car/every day driver, and install a CA18DET for a race/street application

Any thoughts on that?????????